St Eunan’s College is a voluntary Roman Catholic all-male secondary day school (and former boarding school) in County Donegal, Ireland. It is located upon Sentry Hill in Letterkenny. Named after Adomnán or Eunan (the Abbot of Iona who was native to Tír Chonaill, mainly modern County Donegal, and is patron saint of the Roman Catholic Diocese of Raphoe), the school’s foundation stone was laid on the patron saint’s feast day of 23 September.

Its buildings and grounds include the College Chapel, a medial courtyard and playing fields. Architectural features include four turreted round towers and flying buttresses which are modelled on the nearby Cathedral. Sporadic extensions have occurred, including during the early 1930s and the late 1970s — science laboratories and a demonstration room were added in between these two periods of major building work. A monkey puzzle tree grows on the front lawn close to the front door and the College Chapel. Those men who have attended the College are termed Old Adomnánians (/æðɒvˈnɔːnjæns/).

Sportsmen educated there include Olympic athletes, Mark English (a middle-distance runner) and Philip Deignan (a cyclist who later turned professional), as well as several current county footballers, among whom are Michael Murphy, Shaun Patton and Niall O’Donnell. Several members of Cabinet were educated here, including Pa O’Donnell, Neil Blaney and Jim McDaid. Others educated there include quiz player Pat Gibson (Who Wants to Be a Millionaire?, Mastermind, Brain of Britain, Mastermind Champion of Champions, Eggheads), actor Ray McAnally and lexicographer Niall Ó Dónaill.

The College has a tradition since its foundation of hosting musicals, operas, operettas and other performances. Its current principal is Damien McCroary; the All-Ireland-winning Gaelic footballer, Colm McFadden, serves as his deputy. The current manager of the League of Ireland Premier Division Team Finn Harps, Ollie Horgan, is also a teacher at the school