**EXHIBIT 31.1**

**CERTIFICATIONS**

 

I,            Charles W. Fischer, certify that:

 
| 1. | I have reviewed this quarterly report on Form 10-Q of Nexen                        Inc. |
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| 2. | Based on my knowledge, this report does not contain any                        untrue statement of a material fact or omit to state a material fact                        necessary to make the statements made, in light of the circumstances under                        which such statements were made, not misleading with respect to the period                        covered by this report; |
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| 3. | Based on my knowledge, the financial statements, and other                        financial information included in this report, fairly present in all                        material respects the financial condition, results of operations and cash                        flows of the registrant as of, and for, the periods presented in this                        report; |
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| 4. | The registrant’s other certifying officer and I are                        responsible for establishing and maintaining disclosure controls and                        procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and                        internal control over financial reporting (as defined in Exchange Act Rules                        13a-15(f) and 15d-15(f)) for the registrant and we have: |
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|   | (a) | designed such disclosure controls and procedures, or caused                        such disclosure controls and procedures to be designed under our                        supervision, to ensure that material information relating to the                        registrant, including its consolidated subsidiaries, is made known to us by                        others within those entities, particularly during the period in which this                        report is being prepared; |
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|   | (b) | designed such internal control over financial reporting, or                        caused such internal control over financial reporting to be designed under                        our supervision, to provide reasonable assurance regarding the reliability                        of financial reporting and the preparation of financial statements for                        external purposes in accordance with generally accepted accounting                        principles; |
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|   | (c) | evaluated the effectiveness of the registrant’s                        disclosure controls and procedures and presented in this report our                        conclusions about the effectiveness of the disclosure controls and                        procedures, as of the end of the period covered by this report based on                        such evaluation; and |
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|   | (d) | disclosed in this report any change in the                        registrant’s internal control over financial reporting that occurred                        during the registrant’s most recent fiscal quarter (the                        registrant’s fourth fiscal quarter in the case of an annual report)                        that has materially affected, or is reasonably likely to materially affect,                        the registrant’s internal control over financial reporting;                        and; |
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| 5. | The registrant’s other certifying officer and I have                        disclosed, based on our most recent evaluation of internal control over                        financial reporting, to the registrant’s auditors and the audit                        committee of the registrant’s board of directors (or persons                        performing the equivalent function):

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|   | (a) | all significant deficiencies and                        material weaknesses in the design or operation of internal control over                        financial reporting which are reasonably likely to adversely affect the                        registrant’s ability to record, process, summarize and report                        financial information; |
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|   | (b) | any fraud, whether or not material,                        that involves management or other employees who have a significant role in                        the registrant’s internal control over financial                        reporting. |
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| Date: May 1, 2008 |   |   | /s/ Charles W. Fischer                                    |
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|              |   |   | Charles W. Fischer

President and Chief Executive Officer |