Marcus Horan (born 7 September 1977) is a retired Irish rugby union player who played prop for Munster and Ireland.

Horan was educated at Scoil Seanain Naofa (Clonlara National School), St. Munchin's College and Limerick Institute of Technology.

He made his comeback from injury against Edinburgh Rugby on 18 February 2011, and won back the number 1 jersey, starting against Ospreys and Leinster as Munster secured the 2010–11 Magners League.

He missed the 2009 November Tests after having heart surgery, and lost his place to Cian Healy, who held on to the loosehead-prop position during the 2010 Six Nations Championship.

He missed the 2011 Six Nations Championship, but was selected in Ireland's training squad for the 2011 Rugby World Cup warm-ups in August 2011.