Exhibit 12.1**Certification of the Chief Executive Officer**I, Eric Meurice, certify that:1.    I have reviewed this annual report on    Form 20-F of ASML    Holding N.V.;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 company as of, and for, the    periods presented in this report;4.    The company’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    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 accounting principles generally accepted in the    United States of America;  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; and5.    The company’s other certifying officer(s) 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: January 26, 2007/s/ Eric Meurice,Chief Executive OfficerASML ANNUAL REPORT 2006F- 43

 
**Certification of the Chief Financial Officer**I, Peter T.F.M. Wennink, certify that:1.    I have reviewed this annual report on    Form 20-F of ASML    Holding N.V.;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 company as of, and for, the    periods presented in this report;4.    The company’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    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 accounting principles generally accepted in the    United States of America;  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; and5.    The company’s other certifying officer(s) 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: January 26, 2007/s/ Peter T.F.M. WenninkChief Financial OfficerASML ANNUAL REPORT 2006F- 44