Hardon is a surname. Notable people with the surname include:
Eugénie Petain (née Hardon), wife of Maréchal Petain, president of Vichy France John Hardon (1914–2000), Jesuit priest, writer, and theologian Thomas Hardon (1921–present), Australian artist
See also Hadron, a type of composite particle in physics Hard-Ons, an Australian punk rock band Erection of the penis, colloquially called a "hard-on"