Murphy played under Clough at Bramall Lane and again at Burton Albion as the Scot tried to kickstart his career after suffering a serious injury.
“He’s the sort of player who can turn a game in an instant and will supplement our striking options,” said Clough.
“He can play wide or up in the middle in an attacking role, equally effective.
“We’re very excited he’s coming to Mansfield.”
Murphy’s arrival at the Stags followed up a huge coup for Clough after he had already managed to sign midfielder Matty Longstaff from Newcastle United.