Brentwood S. Tolan (November 23, 1855 – June 30, 1923) was an American architect. His most notable works include the National Historic Landmark-designated Allen County Courthouse in downtown Fort Wayne, Indiana, the Whitley County Courthouse in Columbia City, Indiana, the La Porte County Courthouse in La Porte, Indiana, as well as the now-demolished Old National Bank Building and Masonic Temple and Opera House in Fort Wayne.
Tolan was born in Delphos, Ohio to Thomas J. and Harriet Skinner Tolan. With little formal art training, he apprenticed under his father, a marble craftsman-turned architect, starting in 1872 at age 17. In 1874, his father moved the family and architectural practice to Fort Wayne, Indiana.
After his father's death in 1883, Tolan continued the family architectural practice in Fort Wayne. He became well known during the Progressive Era in the Great Lakes area of the Midwest for designing municipal and local government buildings, including courthouses and jails. He later moved to Lima, Ohio, where he practiced with the firm DeCurtin, Rawson, and Tolan. He is buried in Delphos.