Exhibit 12.1

                                  CERTIFICATION

I, Jean P. Cahuzac, certify that:

     1.   I have reviewed this annual report on Form 20-F of Acergy S.A.;

     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.   The company'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 company 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
               company, 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 company'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 company's internal
               control over financial reporting that occurred during the period
               covered by the annual report that has materially affected, or is
               reasonably likely to materially affect, the company's internal
               control over financial reporting; and

     4.   The company's other certifying officer and I have disclosed, based on
          our most recent evaluation of internal control over financial
          reporting, to the company's auditors and the audit committee of the
          company's board of directors (or persons performing the equivalent
          functions):

          (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 company'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 company's
               internal control over financial reporting.


Date: April 23, 2009                         By: /s/    Jean P. Cahuzac
                                          --------------------------------
                                                  Jean P. Cahuzac
                                              Chief Executive Officer