John Dempsey may refer to:
Sports John Dempsey (footballer, born 1946) (1964–2024), Republic of Ireland international football (soccer) player John Dempsey (footballer, born 1951), Tranmere Rovers player John Dempsey (umpire) (born 1965), New Zealand cricket umpire
Politicians John J. Dempsey (1879–1958), American politician, governor of New Mexico John N. Dempsey (1915–1989), American politician, governor of Connecticut
Others John Dempsey (lyricist), also playwright John Dempsey (Medal of Honor) (1848–1884), American sailor and Medal of Honor recipient John Church Dempsey (1802–1877), English portrait artist
See also Jack Dempsey (disambiguation) John Dempsey Hoblitzell, American politician