EXHIBIT 31.1
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CERTIFICATIONS

I, Charles W. Fischer, certify that:

1.    I have reviewed this annual report on Form 10-K 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(s) 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(s) 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
      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:     February 23, 2006             /s/ Charles W. Fischer
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                                        Charles W. Fischer
                                        President, and Chief Executive Officer