Saint Mary's GAC Slaughtmanus (Irish: CLG Naomh Mhuire Leacht Mhanuis) is a Gaelic Athletic Association club based in Slaughtmanus on the outskirts of Derry, County Londonderry, Northern Ireland.

The club is a member of the Derry GAA and currently caters for Gaelic football and Camogie.

Seán Ó Gallchobhair (the curate in Tamnaherin end of the Parish at the time).

After much discussion the two clubs decided that the best thing for the future of the GAA in the area was to amalgamate.

The County Board agreed and St Mary's GAC Slaughtmanus played its first match against Glenullin in March 1979.