Dennis William Sullivan (September 28, 1882 – June 2, 1956) was a center fielder in Major League Baseball who played from 1905 through 1909 for the Washington Senators (1905), Boston Americans / Red Sox (1907–1908) and Cleveland Naps (1908–1909). A native of Hillsboro, Wisconsin, he batted left-handed and threw right-handed. In a four-year career, Sullivan was a .239 hitter (221-for-925) with one home run and 51 RBI in 255 games, including 106 runs, 25 doubles, eight triples, and 30 stolen bases. Sullivan died at the age of 73 in West Los Angeles, California.