Louis Wood Mahaffey
- Bats Right, Throws Unknown
- Height 5' 9", Weight 170 lb.
- Debut April 26, 1898
- Final Game April 26, 1898
- Born January 3, 1874 in Dayton, KY USA
- Died October 26, 1949 in Torrance, CA USA
Lou Mahaffey pitched one game in the majors with the Louisville Colonels on April 26, 1898, on a team that also featured the young Honus Wagner. Lou pitched nine innings, giving up three earned runs and six unearned runs, from a total of ten hits and five walks.
Lou's minor league record is not complete, possibly because he was part of a baseball-playing family. Lou was born in Dayton, KY, across the river from Ohio, while contemporary minor leaguer Joe Mahaffey was also born in Dayton. Another contemporary, James Mahaffey, has an unknown birthplace and contemporary Jack Mahaffey was born in Troy, OH. There are also a number of minor league records attributed only to "Mahaffey", with the obvious difficulty of figuring out which Mahaffey they belong to. Lou, Joe, Jack and James were all pitchers.
It is known that Lou went 30-10 for the 1897 Cedar Rapids Rabbits. It wasn't his first year - he had been playing since at least 1895 in the minors. However, winning 30 games clearly made an impression as he was in the majors the next April. He was back with Cedar Rapids in 1899, and in 1901 played first base for the Portland Webfoots. He was back with Portland for part of 1902.
He was an umpire in the Pacific National League in 1903.