The urban agglomeration of Longueuil was created on January 1, 2006 as a result of the de-amalgamation process brought upon by the Charest government.

It encompasses all the boroughs that were merged into the previous city of Longueuil and still retains the same area as that mega-city.

[4] Longueuil merged on January 1, 2002 with the communities of Boucherville, Brossard, Greenfield Park, LeMoyne, Saint-Bruno-de-Montarville, Saint-Hubert, and Saint-Lambert.

On June 20, 2004, the former boroughs of Boucherville, Brossard, Saint-Bruno-de-Montarville and Saint-Lambert voted to demerge from Longueuil to reconstitute themselves as municipalities on January 1, 2006.

In 2005, the population of LeMoyne was given the choice to pick a new borough between Le Vieux-Longueuil, Saint-Hubert and Greenfield Park.