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 we 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:    April 27, 2007                    /s/ Charles W. Fischer
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                                           Charles W. Fischer
                                           President and Chief Executive Officer