Odhran MacNiallais got the only goal at Kingspan Breffni Park
Donegal and Monaghan must do it all again after a 1-11 to 0-14 draw.
With both sides aiming for an Ulster championship final place in this evening's semi-final at Kingspan Breffni Park, Odhran MacNiallais got the only goal of the game for Donegal.
But they suffered a blow when Martin McElhinney was dismissed.
Ulster SFC Donegal 1-11 Monaghan 0-14 (FT) Going to replay #ulster16— Monaghan GAA (@monaghangaa) June 25, 2016
In a closely-fought contest, Monaghan's Conor McManus also kicked late frees to send the game to a replay.
Monaghan's Owen Duffy and Karl Lacey of Donegal ©INPHO/Andrew Paton
Donegal's Michael Murphy and Vinny Corey of Monaghan ©INPHO/Andrew Paton
Monaghan's Conor McManus and Paddy McGrath with Ciaran Gillespie of Donegal ©INPHO/Andrew Paton
Donegal's Ryan McHugh and Ryan McAnespie of Monaghan ©INPHO/Andrew Paton