<PAGE>

                                                                    EXHIBIT 23.1

            Consent of Independent Registered Public Accounting Firm

We consent to the reference to our firm under the caption "Experts" in the
Registration Statement (Form S-3) and related Prospectus of Illumina, Inc. for
the registration of 1,579,897 shares of its common stock and to the
incorporation by reference therein of our reports dated February 16, 2005, with
respect to the consolidated financial statements and schedule of Illumina, Inc.,
Illumina, Inc. management's assessment of the effectiveness of internal control
over financial reporting, and the effectiveness of internal control over
financial reporting of Illumina, Inc., included in its Annual Report (Form
10-K/A) for the year ended January 2, 2005, filed with the Securities and
Exchange Commission.

                                            /s/ Ernst & Young LLP

San Diego, California
May 16, 2005
