John Duncan Forsyth (1886 or 1887–1963) was a Scottish-American architect who became prominent in Oklahoma. Based in Tulsa and working in a variety of styles, he was connected with a number of significant buildings around the state.
According to one source, Forsyth was born in 1886 in Florence, Italy; another source says he was born in 1887 in Kingskettle, Fife, Scotland. He was raised in Scotland and studied at Edinburgh College, and at the Sorbonne and L’Ecole des Beaux-Arts in Paris.
He immigrated to the United States in 1908. He was a member of the large team of architects who worked on Central Union Station (now the Government Conference Centre) in Ottawa. He trained with various architects, including John Russell Pope. during World War I, he fought with the Royal Flying Corps.
In 1921 Forsyth moved to Tulsa, Oklahoma, where he became associated with Tulsa architect John McDonnell He received his Oklahoma architect's license in 1925. Soon he was hired for what became one of his most famous buildings, the E. W. Marland Mansion in Ponca City. The Marland mansion, which is operated as a museum, includes a room dedicated to Forsyth's work.
Forsyth maintained a prolific practice. During World War II, he left Oklahoma to serve with the U.S. Navy Seabees in California and worked there after the war. In the 1950s, he returned to Tulsa. He had been married a total of six times. Forsyth remained in Tulsa until his death in 1963.