Ruan Pienaar kicked 15 points as Montpellier cut loose in the second half to thrash Pau 45-13 and make it 13 straight league victories at home this term.
Toulon booked its place in the play-offs with a 59-13 victory over Castres that lifted it up to second, Josua Tuisova scoring two of its seven tries as it moved ahead of Toulouse and Racing 92, which both play on Monday (AEST).
Lyon still sits fifth despite a 39-18 defeat away at Oyonnax, which remains in danger of featuring in a relegation play-off despite the impressive result in the penultimate round of fixtures.
Oyonnax is 13th in the standings, three points behind a Stade side that condemned Brive to the drop with a 30-22 triumph over the competition's bottom club.
Jules Plisson scored a try, kicked a conversion and also landed five penalties for the Paris heavyweight, although it is still not certain of retaining its top-flight status.
Agen, however, is safe thanks to a 27-17 win over Clermont Auvergne, which had Sebastien Vahaamahina sent off in the first half.