The Irwin Library is one of the three libraries operated by Butler University, Indianapolis, United States. Minoru Yamasaki was the lead architect, and constructed the library in the architectural style of New Formalism. Construction of the library cost $2.25 million, of which $1.5 million was underwritten by the Irwin-Sweeney-Miller foundation. After construction was finished, the library's first day of operation was on September 9, 1963. The library was named in honor of William G. Irwin, who served as a trustee of Butler University from 1908 until his death in 1943.