St Pat's suffered their second consecutive defeat for the first time in the league this season.
The Saints were two down at half-time but couldn't add to Chris Forrester's second half goal.
The Saints now face Cork City at home next Friday in the last league match of the season and need a point to guarantee Europa League football next season.
|11||St. Patrick's Athletic||10||8|
|12||Galway United FC||9||5|