Wintrust Financial (WTFC) S-4 Registration of securities issued in business combination transactions

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-4) and related Proxy Statement/Prospectus of Wintrust Financial Corporation for the approval of the merger agreement between Wintrust Financial Corporation and Hinsbrook Bancshares, Inc. and to the incorporation by reference therein of our report dated March 4, 2005, with respect to the consolidated financial statements of Wintrust Financial Corporation included in its Annual Report (Form 10-K) for the year ended December 31, 2004, filed with the Securities and Exchange Commission.

/s/ ERNST & YOUNG LLP  

ERNST & YOUNG LLP 

Chicago, Illinois
January 4, 2006