- Loïs Openda (31')
The Belgium striker found the back of the net for the 15th time this season in the league to put the northerners on 60 points from 29 games, ahead of OM on goal difference after the Provence side drew 1-1 with Montpellier on Friday.
Paris Saint-Germain lead the standings on 66 points before hosting Lyon on Sunday.
Rennes are fifth on 50 points.
Lens, who are back on track after a four-match winless streak in February, went ahead in the 31st minute when Openda headed home from Florian Sotoca's cross for his sixth goal in his last three Ligue 1 games.
Sekou Fofana came close to doubling Lens's advantage in the second half, but his header went wide.
Keeper Brice Samba then made sure the visitors would leave the Roazhon Park with all three points with a couple of fine saves to deny Arnaud Kalimuendo and Bourigeaud as Franck Haise's team secured their third win in a row.
- Clément Turpin
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