'''Gainer''' is a surname. Notable people with the name include:
* Aaron Gainer, member of American Christian post-grunge band '12 Stones' * Alice Gainer (born 1982), American television reporter * Amari Gainer (born 2000), American football player * Del Gainer (1886–1947), American baseball player * Derrick Gainer (American football) (born 1966), American football player * Derrick Gainer (born 1972), American boxer * Sir Donald Gainer (1891–1966), British ambassador * Elmer Gainer (1918–1970), American basketball player * Forrest Gainer (born 1979), Canadian rugby player * Frank Gainer (1888–1975), Canadian politician * Glen Gainer Jr. (1927–2009), American politician * Glen Gainer III (born 1960), American politician * Jay Gainer (born 1966), American baseball player * John L. Gainer (born 1938), American chemical engineer * Ronald William Gainer (born 1947), American Catholic priest, appointed Bishop of Harrisburg in 2014 * Steve Gainer (born 1962), American cinematographer * Terrance W. Gainer (born 1947), Sergeant at Arms of the United States Senate 2007–14
{{surname|Gainer}}