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UNITED STATES SECURITIES AND EXCHANGE COMMISSION
 WASHINGTON, D.C. 20549
 FORM 20-F
 Annual report pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934
 For the fiscal year ended December 31, 2005
Commission file number 1-9159
 NORSK HYDRO ASA
  
 
  Title of Each Class
    
    Name of Each ExchangeAmerican Depositary Shares
    
    on Which RegisteredNew York Stock ExchangeOrdinary Shares, par value
    
    New York Stock Exchange*NOK 18.30 per share
 
  
  Ordinary Shares, par value NOK 18.30 per share
  250,138,464 Ordinary Shares, par value NOK 18.30 per share
  þ o
  o þ
  þ o
  þ o o
  o þ
  o þ
 *
    
    Not for trading, but only in connection
with the registration of American Depositary Shares pursuant to the
requirements of the Securities and Exchange Commission.




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ITEM 1. IDENTITY OF DIRECTORS, SENIOR MANAGEMENT AND ADVISERS
 Not applicable.
 ITEM 2. OFFER STATISTICS AND EXPECTED TIMETABLE
 Not applicable.
 ITEM 3. KEY INFORMATION
 3.A.
    
    Selected financial data.The information set forth under the headings Business and Operating
Information  Financial Information  Selected Consolidated Financial Data on page
42 and Risk, Regulation and Other Information  Other Information  Exchange Rate
Information on page 104 of the Companys Annual Report and Form 20-F 2005 contained
in the Companys Report on Form 6-K dated March 24, 2006, is incorporated herein by
reference.3.B.
    
    Capitalization and Indebtedness.Not applicable.3.C.
    
    Reasons for the offer and use of proceeds.Not applicable.3.D.
    
    Risk factors.The information set forth under the heading Risk, Regulation and Other
Information  Risk Factors on pages 92 to 96 of the Companys Annual Report and
Form 20-F 2005 contained in the Companys Report on Form 6-K dated March 24, 2006,
is incorporated herein by reference.
 ITEM 4. INFORMATION ON THE COMPANY
 4.A.
    
    History and development of the company.The information set forth under the headings Business and Operating
Information  About Hydro on pages 8 to 10, Business and Operating Information 
History and Development of the Company on page 11, Business and Operating
Information  Other Information on page 11, Business and Operating Information 
Financial Information  Investments on page 61, Business and Operating Information
 Financial Information  Material commitments for capital expenditures on page 61,
Appendix F: Financial Statements and Other Information  Note 2: Business
combinations, dispositions and demerger on pages F14-F16 and Appendix T: Terms and
Definitions on pages T2-T4 of the Companys Annual Report and Form 20-F 2005
contained in the Companys Report on Form 6-K dated March 24, 2006, is incorporated
herein by reference.4.B.
    
    Business overview.The information set forth under the headings Business and Operating
Information on pages 8 to 41, Risk, Regulation and Other Information  Government
Regulation and Taxation on pages 97 to 101, Society, People, Environment, on
pages 84 and 86 to 90, Appendix O: Operating Statistics on pages O2-O3, Use of
Non-GAAP Financial Measures on pages F60-F66 and Cautionary Note in relation to
Certain Forward-Looking Statements on the back cover of the Companys Annual Report
and Form 20-F 2005 contained in the Companys Report on Form 6-K dated March 24,
2006, is incorporated herein by reference.




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4.C.
    
    Organizational structure.The information set forth under the heading Business and Operating Information
 About Hydro  Organization (chart) on page 9 of the Companys Annual Report and
Form 20-F 2005 contained in the Companys Report on Form 6-K dated March 24, 2006,
is incorporated herein by reference.4.D.
    
    Property, plants and equipment.The information set forth under the headings Business and Operating
Information on pages 8 to 41, Risk, Regulation and Other Information  Government
Regulation and Taxation on pages 97 to 101 and Appendix F: Financial Statements
and Other Information  Note 15: Property, plant and equipment on page F33 of the
Companys Report in the Companys Annual Report and Form 20-F 2005 on Form 6-K dated
March 24, 2006, is incorporated herein by reference.
 ITEM 4A. UNRESOLVED STAFF COMMENTS
 Not applicable.
 ITEM 5. OPERATING AND FINANCIAL REVIEW AND PROSPECTS
 5.A.
    
    Operating results.The information set forth under the headings Business and Operating
Information  Financial Information  Financial Review on pages 43 to 57, Business
and Operating Information  Financial Information  Hydros Critical Accounting
Policies on pages 62 to 64, IFRS in Hydros Financial Statements on page F67,
Use of Non-GAAP Financial Measures on pages F60 to F66, Appendix T: Terms and
Definitions on pages T2 to T4 and Cautionary Note in relation to Certain
Forward-Looking Statements on the back cover of the Companys Annual Report and
Form 20-F 2005 contained in the Companys Report on Form 6-K dated March 24, 2006,
is incorporated herein by reference.5.B.
    
    Liquidity and capital resources.The information set forth under the heading Business and Operating Information
 Financial Information  Liquidity and Capital Resources on pages 58 to 61 of the
Companys Annual Report and Form 20-F 2005 contained in the Companys Report on Form
6-K dated March 24, 2006, is incorporated herein by reference.5.C.
    
    Research and development, patents and licenses, etc.The information set forth under the heading Business and Operating Information
 Research and Development on page 67 of the Companys Annual Report and Form 20-F
2005 contained in the Companys Report on Form 6-K dated March 24, 2006, is
incorporated herein by reference.5.D.
    
    Trend information.The information set forth under the heading Business and Operating Information
 Financial Information  Financial Review on pages 43 to 64 of the Companys
Annual Report and Form 20-F 2005 contained in the Companys Report on Form 6-K dated
March 24, 2006, is incorporated herein by reference.




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5.E.
    
    Off-balance sheet arrangements.The information set forth under the heading Business and Operating Information
 Financial Information  Contractual obligations, commitments and off-balance sheet
arrangements on page 60 of the Companys Annual Report and Form 20-F 2005 contained
in the Companys Report on Form 6-K dated March 24, 2006, is incorporated herein by
reference.5.F.
    
    Tabular disclosure of contractual obligations.The information set forth under the heading Business and Operating Information
 Financial Information  Contractual Obligations (table) on page 60 of the
Companys Annual Report and Form 20-F 2005 contained in the Companys Report on Form
6-K dated March 24, 2006, is incorporated herein by reference.5.G.
    
    Safe harborThe information set forth under the heading Cautionary Note in relation to
Certain Forward-Looking Statements on the back cover of the Companys Annual Report
and Form 20-F 2005 contained in the Companys Report on Form 6-K dated March 24,
2006, is incorporated herein by reference.
 ITEM 6. DIRECTORS, SENIOR MANAGEMENT AND EMPLOYEES
 6.A.
    
    Directors and senior management.The information set forth under the headings Investor Information  Corporate
Governance  Board of Directors on page 80 and Investor Information  Corporate
Governance  Corporate Management Board on page 81 of the Companys Annual Report
and Form 20-F 2005 contained in the Companys Report on Form 6-K dated March 24,
2006, is incorporated herein by reference.6.B.
    
    Compensation.The information set forth under the headings Investor Information  Corporate
Governance  Directors and Officers Compensation, Share Ownership and Loans on
page 77 and Appendix F: Financial Statements and Other
Information  Note 4: Remuneration and Share-Based Compensation on page F19 of the Companys Annual
Report and Form 20-F 2005 contained in the Companys Report on Form 6-K dated March
24, 2006, is incorporated herein by reference.6.C.
    
    Board practices.The information set forth under the heading Investor Information  Corporate
Governance  Governance Bodies on pages 74 to 79 of the Companys Annual Report and
Form 20-F 2005 contained in the Companys Report on Form 6-K dated March 24, 2006,
is incorporated herein by reference.6.D.
    
    Employees.The information set forth under the headings Society, People, Environment 
Facts and Figures  Geographical distribution of employees and payroll (table) on
page 86 and Society, People, Environment  Facts and Figures  People on page 87
of the Companys Annual Report and Form 20-F 2005 contained in the Companys Report
on Form 6-K dated March 24, 2006, is incorporated herein by reference.




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6.E.
    
    Share ownership.The information set forth under the headings Investor Information  Corporate
Governance  Directors and officers compensation, share ownership and loans on page
77 and Appendix F: Financial Statements and Other
Information  Note 4: Remuneration and Share-based Compensation on page F19 of the Companys Annual
Report and Form 20-F 2005 contained in the Companys Report on Form 6-K dated March
24, 2006, is incorporated herein by reference.
 ITEM 7. MAJOR SHAREHOLDERS AND RELATED PARTY TRANSACTIONS
 7.A.
    
    Major shareholders.The information set forth under the heading Investor Information  Shareholder
Information  Major shareholders and voting rights on page 72 of the Companys
Annual Report and Form 20-F 2005 contained in the Companys Report on Form 6-K dated
March 24, 2006, is incorporated herein by reference.7.B.
    
    Related party transactions.The information set forth under the headings Appendix F: Financial Statements
and Other Information  Note 4: Remuneration and Share-based Compensation on page
F19, Appendix F: Financial Statements and Other
Information  Note 13: Non-consolidated Investees on page F31 and Investor Information  Corporate
Governance  Governance Bodies  Board of Directors on pages 78 to 79 of the
Companys Annual Report and Form 20-F 2005 contained in the Companys Report on Form
6-K dated March 24, 2006, is incorporated herein by reference.7.C.
    
    Interests of experts and counsel.Not applicable.
 ITEM 8. FINANCIAL INFORMATION
 8.A.
    
    Consolidated Statements and Other Financial Information.The information set forth under the headings Appendix F: Financial Statements
and Other Information  Consolidated Financial Statements US GAAP on pages F3 to
F5, Appendix F: Financial Statements and Other Information  Notes 1-27 on pages
F8 to F49, Business and Operating Information  Other  Legal Proceedings on page
68 and Investor Information  Shareholder Information  Dividend Policy on page 70
of the Companys Annual Report and Form 20-F 2005 contained in the Companys Report
on Form 6-K dated March 24, 2006, is incorporated herein by reference.8.B.
    
    Significant Changes.None.
 ITEM 9. THE OFFER AND LISTING
 9.A.
    
    Offer and listing details.The information set forth under the heading Investor Information  Shareholder
Information  Key Figures for the Hydro share on pages 72 to 73 of the Companys
Annual Report and Form 20-F 2005 contained in the Companys Report on Form 6-K dated
March 24, 2006, is incorporated herein by reference.




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9.B.
    
    Plan of distribution.Not applicable.9.C.
    
    Markets.The information set forth under the heading Investor Information  Shareholder
Information on page 70 of the Companys Annual Report and Form 20-F 2005 contained
in the Companys Report on Form 6-K dated March 24, 2006, is incorporated herein by
reference.9.D.
    
    Selling shareholders.Not applicable.9.E.
    
    Dilution.Not applicable.9.F.
    
    Expenses of the issue.Not applicable.
 ITEM 10. ADDITIONAL INFORMATION
 10.A.
    
    Share capital.Not applicable.10.B.
    
    Memorandum and articles of association.Incorporated by reference from Item 10.B (Articles of Association) on pages
125 to 133 of the Companys 2004 20-F filed on March 18, 2005.10.C.
    
    Material contracts.Not applicable.10.D.
    
    Exchange controls.The information set forth under the heading Risk, Regulation and Other
Information  Other Information  Exchange Controls on page 104 of the Companys
Annual Report and Form 20-F 2005 contained in the Companys Report on Form 6-K dated
March 24, 2006, is incorporated herein by reference.10.E.
    
    Taxation.The information set forth under the heading Risk and Regulation and Other
Information  Other Information  Taxation on pages 102 to 103 of the Companys
Annual Report and Form 20-F 2005 contained in the Companys Report on Form 6-K dated
March 24, 2006, is incorporated herein by reference.10.F.
    
    Dividends and paying agents.Not applicable.




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10.G.
    
    Statement by experts.Not applicable.10.H.
    
    Documents on display.Not applicable.10.I.
    
    Subsidiary Information.Not applicable.
 ITEM 11. QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK
 The information set forth under the heading Business and Operating Information 
Other  Market Risk on pages 65 to 66 of the Companys Annual Report and Form 20-F
2005 contained in the Companys Report on Form 6-K dated March 24, 2006, is
incorporated herein by reference.
 ITEM 12. DESCRIPTION OF SECURITIES OTHER THAN EQUITY SECURITIES
 Not applicable.
 ITEM 13. DEFAULTS, DIVIDEND ARREARAGES AND DELINQUENCIES
 None.
 ITEM 14. MATERIAL MODIFICATIONS TO THE RIGHTS OF SECURITY HOLDERS AND USE
OF PROCEEDS
 None.
 ITEM 15. CONTROLS AND PROCEDURES
 The information set forth under the heading Investor Information  Corporate
Governance  Controls and Procedures on pages 75 to 76 of the Companys Annual
Report and Form 20-F 2005 contained in the Companys Report on Form 6-K dated March
24, 2006, is incorporated herein by reference.
 ITEM 16A. AUDIT COMMITTEE FINANCIAL EXPERT
 The information set forth under the heading Investor Information  Corporate
Governance  Governance Bodies  Audit Committee on page 79 of the Companys Annual
Report and Form 20-F 2005 contained in the Companys Report on Form 6-K dated March
24, 2006, is incorporated herein by reference.
 ITEM 16B. CODE OF ETHICS
 The information set forth under the heading Investor Information  Corporate
Governance  Corporate Directives and Code of Conduct on pages 74 to 75 of the
Companys Annual Report and Form 20-F 2005 contained in the Companys Report on Form
6-K dated March 24, 2006, is incorporated herein by reference.
 ITEM 16C. PRINCIPAL ACCOUNTANT FEES AND SERVICES
 The information set forth under the headings Appendix F: Financial Statements and
Other Information  Note 25: External audit remuneration on page F43, Investor
Information 




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Corporate Governance  Governance Bodies  Audit Committee on page 79
and Investor Information  Corporate Governance  Pre-Approval of Audit Services
on page 76 of the Companys Annual Report and Form 20-F 2005 contained in the
Companys Report on Form 6-K dated March 24, 2006, is incorporated herein by
reference.
 ITEM 16D. EXEMPTIONS FROM THE LISTING STANDARDS FOR AUDIT COMMITTEES
 Not applicable.
 ITEM 16E. PURCHASES OF EQUITY SECURITIES BY THE ISSUER AND AFFILIATED
PURCHASERS
 The information set forth under the headings Investor Information  Shareholder
Information  Buyback of shares on pages 70 to 71 and Appendix F: Financial
Statements and Other Information  Note 26: Related parties and Variable Interest
Entities on page F43 of the Companys Annual Report and Form 20-F 2005 contained in
the Companys Report on Form 6-K dated March 24, 2006, is incorporated herein by
reference.
 ITEM 17. FINANCIAL STATEMENTS
 Not applicable.
 ITEM 18. FINANCIAL STATEMENTS
 REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRMTo the Board of Directors and shareholders of Norsk Hydro ASAOslo, NorwayWe have audited the consolidated balance sheets of Norsk Hydro ASA and subsidiaries
as of 31 December 2005 and 2004, and the related consolidated income statements,
statements of comprehensive income, and cash flows for each of the three years in
the period ended 31 December 2005. Our audits also included the financial statement
schedule included at Item 15(a). These financial statements and the financial
statement schedule are the responsibility of the Companys management. Our
responsibility is to express an opinion on these financial statements and the
financial statement schedule based on our audits.We conducted our audits in accordance with the standards of the Public Company
Accounting Oversight Board (United States). Those standards require that we plan
and perform the audit to obtain reasonable assurance about whether the financial
statements are free of material misstatement. The Company is not required to have,
nor were we engaged to perform, an audit of its internal control over financial
reporting. Our audits included consideration of internal control over financial
reporting as a basis for designing audit procedures that are appropriate in the
circumstances, but not for the purpose of expressing an opinion on the effectiveness
of the Companys internal control over financial reporting. Accordingly, we express
no such opinion. An audit also includes examining, on a test basis, evidence
supporting the amounts and disclosures in the financial statements, assessing the
accounting principles used and significant estimates made by management, as well as
evaluating the overall financial statement presentation. We believe that our audits
provide a reasonable basis for our opinion.In our opinion, such consolidated financial statements present fairly, in all
material respects, the financial position of Norsk Hydro ASA and subsidiaries as of
31 December 2005 and 2004, and the results of their operations and their cash flows for each of the three
years in the period ended 31 December 2005 in conformity with accounting principles
generally accepted in the United States of America. Also, in our opinion, the
financial statement schedule, when




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considered in relation to the basic consolidated
financial statements taken as a whole, presents fairly in all material respects the
information set forth therein.As discussed in Note 1 to the financial statements, the Company changed its method
of accounting for contingent asset retirement obligations in 2005, variable interest
entities in 2004 and asset retirement obligations in 2003 to conform to newly
adopted accounting principles./s/ Deloitte Statsautoriserte Revisorer ASOslo, Norway7 March 2006The information set forth under the headings Appendix F: Financial Statements and
Other Information  Consolidated Financial Statements US GAAP on pages F3 to F5 and
Appendix F: Financial Statements and Other Information  Notes 1-27 on pages F8 to
F49 of the Companys Annual Report and Form 20-F 2005 contained in the Companys
Report on Form 6-K dated March 24, 2006, is incorporated herein by reference.
 ITEM 19. EXHIBITS
 1.1
    
    
    Articles of Association of Norsk Hydro ASA*4.(b).1
    
    
    Agreement and Plan of Merger, dated September 18, 2005, among Norsk Hydro
ASA, Norsk Hydro E&P Americas, L.P., Harald Acquisition Corp., and Spinnaker
Exploration Company.**4.(c).1
    
    
    Option Plan for Selected Members of Hydros Top Management Group: 2005-2011.4.(c).2
    
    
    Option Plan for Selected Members of Hydros Top Management Group: 2004-2010.4.(c).3
    
    
    Executive Share Option Plan 2003.4.(c).4
    
    
    Executive Share Option Plan 2002.4.(c).5
    
    
    Employee Contract, dated October 15, 2004, between Eivind Reiten, CEO, and
Norsk Hydro ASA.***8
    
    
    A list of the Companys principal subsidiary undertakings,
indicating their country of incorporation and the names under which they do
business.****12.1
    
    
    Certification of Eivind Reiten, President and Chief Executive
Officer of Norsk Hydro ASA, pursuant to Section 13(a) of the Securities
Exchange Act of 1934, as amended, as adopted pursuant to Section 302 of the
Sarbanes-Oxley Act of 2002.12.2
    
    
    Certification of John Ove Ottestad, Executive Vice President
and Chief Financial Officer of Norsk Hydro ASA, pursuant to Section 13(a) of
the Securities Exchange
Act of 1934, as amended, as adopted pursuant to Section 302 of the
Sarbanes-Oxley Act of 2002.
 
 *
    
    Previously filed as an exhibit to the
Companys 2004 20-F filed on March 18, 2005.**
    
    Previously filed as an exhibit to the
Companys Schedule 13D filed September 19, 2005.***
    
    Previously filed as an exhibit to the
Companys 2004 20-F filed on March 18, 2005.****
    
    Previously filed as an exhibit to the
Companys 2004 20-F filed on March 18, 2005.




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13
    
    
    Certifications of Eivind Reiten, President and Chief Executive
of Norsk Hydro ASA, and John Ove Ottestad, Executive Vice President and Chief
Financial Officer of Norsk Hydro ASA, pursuant to 18 U.S.C. 1350, as adopted
pursuant to Section 906 of the Sarbanes-Oxley Act of 200215.(a).1
    
    
    Consent of Deloitte Statsautoriserte Revisorer AS, independent registered
public accounting firm of Norsk Hydro ASA.15.(b).1
    
    
    Valuation and Qualifying Accounts and Reserves.15.(b).2
    
    
    The Companys responses to the requirements of Form 20-F have been
incorporated by reference to the Companys Report on Form 6-K dated March 24,
2006 which contains the Norsk Hydro ASA Annual Report and Form 20-F 2005.
Pursuant to Rule 12b-23(a) of the Securities Exchange Act of 1934, as amended,
the information incorporated into this report by reference to such Report on
Form 6-K is attached as an exhibit hereto.




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Date: 24 March 2006Norsk Hydro ASARegistrantBy: /s/      John O. OttestadName: John O. OttestadTitle: Executive Vice President
and
       Chief Financial Officer




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EXHIBIT INDEX
 1.1
    
    Articles of Association of Norsk Hydro ASA*4.(b).1
    
    Agreement and Plan of Merger, dated September 18, 2005, among Norsk Hydro ASA, Norsk Hydro
E&P Americas, L.P., Harald Acquisition Corp., and Spinnaker Exploration Company.**4.(c).1
    
    Option Plan for Selected Members of Hydros Top Management Group: 2005-2011.4.(c).2
    
    Option Plan for Selected Members of Hydros Top Management Group: 2004-2010.4.(c).3
    
    Executive Share Option Plan 2003.4.(c).4
    
    Executive Share Option Plan 2002.4.(c).5
    
    Employment Contact, dated October 15, 2004, between Eivind Reiten, CEO, and Norsk Hydro
ASA.***8
    
    A list of the Companys principal subsidiary undertakings, indicating their country of
incorporation and the names under which they do business.****12.1
    
    Certification of Eivind Reiten, President and Chief Executive Officer of Norsk Hydro ASA,
pursuant to Section 13(a) of the Securities Exchange Act of 1934, as amended, as adopted
pursuant to Section 302 of the Sarbanes-Oxley Act of 200212.2
    
    Certification of John Ove Ottestad, Executive Vice President and Chief Financial Officer of
Norsk Hydro ASA, pursuant to Section 13(a) of the Securities Exchange Act of 1934, as amended,
as adopted pursuant to Section 302 of the Sarbanes-Oxley Act of 200213
    
    Certifications of Eivind Reiten, President and Chief Executive of Norsk Hydro ASA and John
Ove Ottestad, Executive Vice President and Chief Financial Officer of Norsk Hydro ASA,
pursuant to 18 U.S.C. 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of
200215.(a).1
    
    Consent of Deloitte Statsautoriserte Revisorer AS, independent registered public
accounting firm of Norsk Hydro ASA15.(b).1
    
    Valuation and Qualifying Accounts and Reserves15.(b).2
    
    The Companys responses to the requirements of Form 20-F have been incorporated by
reference to the Companys Report on Form 6-K dated March 24, 2006 which contains the Norsk
Hydro ASA Annual Report and Form 20-F 2005. Pursuant to Rule 12b-23(a) of the Securities
Exchange Act of 1934, as amended, the information incorporated into this report by reference
to such Report on Form 6-K is attached as an exhibit hereto.
 
 *
    
    Previously filed as an exhibit to the
Companys 2004 20-F filed on March 18, 2005.**
    
    Previously filed as an exhibit to the
Companys Schedule 13D filed September 19, 2005.***
    
    Previously filed as an exhibit to the
Companys 2004 20-F filed on March 18, 2005.****
    
    Previously filed as an exhibit to t he
Companys 2004 20-F filed on March 18, 2005.