L'Union (French pronunciation: [lynjɔ̃] ⓘ; Occitan: Sent Joan le Nòu) is a commune in the Haute-Garonne department in southwestern France.

The name Saint-Jean-de-l'Union is still spoken of, recalling the time when the communes of Saint-Jean et L'Union were unified.

The D888 (Route d'Albi) road runs through the town in a south-west direction towards Toulouse and north-east to Albi, roughly 75 kilometres away.

The A68 motorway (Toulouse-Albi) and the Périphérique bypass the south of L'Union, served by Junctions 1 and 14 respectively.

In a clockwise order, L'Union is bordered by Toulouse, Launaguet, Saint-Geniès-Bellevue, Saint-Jean, Montrabé and Balma.