William Holabird (September 11, 1854, Amenia, New York - July 19, 1923, Evanston, Illinois) was an American architect.
Holabird studied at the United States Military Academy at West Point but resigned and moved to Chicago, where he later got married. He worked for William Le Baron Jenney. He established the firm of Holabird & Simonds in 1880 with Ossian Simonds, another draftsman from Jenney's office. Martin Roche joined him in 1881, and shortly afterward Graceland Cemetery became one of their first commissions. Simonds left the practice in 1883 to concentrate on landscape design, and the firm was renamed Holabird & Roche.
Together they contributed many innovations to the architecture of the time, especially in what is now referred to as Chicago School. They designed several influential buildings, including the Marquette Building and the Gage Building. The latter included a façade designed by Louis Sullivan and was cited a Chicago architectural landmark in 1962.
William Holabird died in 1923, and Martin Roche died in 1927. Holabird's son John took over the firm with John Wellborn Root, Jr., and it was renamed Holabird & Root.
William's sister Agnes Holabird Von Kurowsky is the mother of Agnes von Kurowsky.