Mons-en-Barà Âul () is a commune in the Nord department in northern France.
It is a suburb of the city of Lille, and is adjacent to it on the northeast. The name Mons-en-Barà Âul means mount in the Barà Âul, the city is built on a slight hill; the Barà Âul was a former territory (see also Marcq-en-Barà Âul). Before the sixteenth century, little is known of this county, which was only rural. Plans of the eighteenth century show Mons-en-Barà Âul as a small village without a church, with farms scattered along the high road from Lille to Roubaix. It is a former dependency of Fives, a district which is now part of Lille.