John Dwight Chesbro (June 5, 1874 – November 6, 1931) was a Major League Baseball pitcher at the turn of the 20th century. He was nicknamed "Happy Jack". Chesbro, a spitballer (spitballs were legal until 1920), broke into the majors in 1899 with the Pittsburgh Pirates. He pitched for the Pirates until 1902 and in his final year went an astonishing 28-6 with a 2.17 ERA. Chesbro retired in 1909, having accumulated a 198-132 career record and been part of two pennant-winning teams (in 1901 and 1902).