Frank Ellsworth Doremus (August 31, 1865 – September 4, 1947) was an American politician who was the 49th Mayor of Detroit and a member of the U.S. House of Representatives from Michigan.

[2] Frank Doremus attended the public schools of Portland and graduated from Detroit College of Law.

[2] In 1890, Doremus was elected to the Michigan House of Representatives from Ionia County's 1st District serving from 1890 to 1892.

[1] In 1910, Doremus defeated incumbent Republican Edwin C. Denby to be elected as a Democrat from Michigan's 1st congressional district to the Sixty-second and to the four succeeding Congresses, serving from March 4, 1911, to March 3, 1921,[1] and was elected chair of the Democratic Congressional Campaign Committee in 1913.

He served as mayor of Detroit in 1923, defeating former Detroit Police Commissioner Dr. James W. Inches in the general election, until he resigned the following year due to ill-health.