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.A fine outfielder with a light bat, Sullivan went 0-for-11 in his rookie season for the Senators.