EXHIBIT 31.1
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CERTIFICATIONS

I, Charles W. Fischer, certify that:

1.   I have reviewed this quarterly report on Form 10-Q of Nexen Inc.

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;

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;

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 have:

     (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;

     (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;

     (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

     (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;

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):

     (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; and

     (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.


Date:    May 1, 2006                            /s/ Charles W. Fischer
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                                                Charles W. Fischer
                                                President and Chief Executive
                                                Officer