Jacob Leland Niemes (October 19, 1919 – March 4, 1966) was a professional baseball player. He was a left-handed pitcher for one season (1943) with the Cincinnati Reds. For his career, he pitched in three games and recorded no decisions, with a 6.00 earned run average, and 1 strikeout in three innings pitched.
An alumnus of the University of Cincinnati, he was born in Cincinnati, Ohio, and later died in Hamilton, Ohio, at the age of 46.