Frederick Lincoln Siddons (November 21, 1864 – June 19, 1931) was a United States federal judge.
Born in London, England, Siddons received an LL.B. from Columbian University in 1887 and an LL.M. from that institution in 1888. He was a Professor of Law at National University beginning in 1898. He worked for the U.S. Department of Treasury in 1888, and was thereafter in private practice in Washington, D.C.. He was a member of the Commission on Uniform State Laws for the District of Columbia, and in 1913 became a Commissioner for the U.S. District Court for the District of Columbia.
On December 9, 1914, Siddons was nominated by President Woodrow Wilson to a seat on the United States District Court for the District of Columbia vacated by Daniel Thew Wright. Siddons was confirmed by the United States Senate on January 15, 1915, and received his commission the same day. He served until his death, in Washington, D.C.