Frederick Theodore Underwood (October 14, 1868 – January 26, 1906) was a Major League Baseball pitcher during part of the 1894 season. He was a native of St. Louis County, Missouri. Underwood appeared in seven games for the Brooklyn Grooms of the National League, starting six of them and completing five. He gave up 110 baserunners (80 hits and 30 walks) in just 47 innings. He also gave up 62 runs, but only 41 of them were earned runs. In his short MLB career he was 2–4 with 10 strikeouts and an ERA of 7.85. Underwood died at the age of 37 in Kansas City, Missouri.