Four different scorers sealed victory for the home side.
Lorient went 3-0 up by half time through goals from Julien Querica, Yann Jouffre and Wesley Lautoa.
They continued their dominance after the break and Gilles Sunu sealed an impressive victory for the hosts on 81 minutes.
The win was Lorient’s first in three games as they remain in eighth position and move two points closer to Montpellier above them.
The defeat means Brest are still not clear of the relegation zone.
Watch the highlights below.