Montpellier defeated Stade Toulousain 32-22 to take the lead in the Top 14 after Lyon lost at Clermont on Saturday.
A brace of Alivereti Raka tries, together with scores from David Strettle, Morgan Parra and Sitaleki Timani, helped reigning champions Clermont dispatch visitors Lyon 39-18 at the Stade Marcel-Michelin.
And the result saw Lyon displaced from the summit later in the day, as Jan Serfontein, Gabriel Ngandebe, Jesse Mogg and Joe Tomane all crossed for Montpellier at home to Toulouse.
The boot of Zack Holmes kept the away team in touch at Altrad Stadium, but they could only muster one 65th-minute try from Maks van Dyk.
Elsewhere, third-placed La Rochelle also slipped up, succumbing to a first-half onslaught to lose 31-15 at Castres Olympique, who scored three tries in the first 24 minutes to lead 21-3 at the break.
Bordeaux Begles in fifth saw off struggling Agen 33-23 at home and Section Paloise defeated second-bottom side Brive 34-15.