The French champions saw two points slip from their grasp when a last-minute Jimmy Briand goal cancelled out Kim Kallstrom's 66th-minute opener.
Lyon have 53 points from 26 games with rivals PSG (49 points), Olympique Marseille (48) and Girondins Bordeaux (47) in close pursuit after they all won at the weekend.
Rennes, who had a Carlos Bocanegra goal disallowed in the first half, stepped up another gear after the interval but John Mensah denied Briand after the striker had dribbled past Lyon keeper Hugo Lloris.
Briand was once again alone in front of Lloris in the 66th minute but the French international keeper parried his powerful volley.
In the resulting counter-attack, Kallstrom found the top corner of Nicolas Douchez's goal with an angled shot from the edge of the box.
Rennes, though, did not let go and Briand finally got the better of Lloris with a lob after being set up by defender Petter Hansson.
IMPRESSIVE TRIO
Earlier on Sunday, Hoarau, Ludovic Giuly and Stephane Sessegnon were once again impressive for PSG at the Parc des Princes.
The home side were 2-0 up after only 13 minutes, striker Hoarau heading home on 10 minutes from a Jerome Rothen free kick and diminutive winger Giuly doubling the tally three minutes later when he latched on to a Sessegnon cross.
A blunder by Mickael Landreau, though, put the visitors back in the game when Feret was quicker to the ball than the PSG keeper to reduce the arrears with a fine lob.
Hoarau restored PSG's two-goal lead five minutes from the interval, beating Gennaro Bracigliano from close range.
Sessegnon completed the rout shortly after the hour when he brought down a Hoarau cross from the left to coolly slot the ball past Bracigliano.
The Benin midfielder, however, will be sorely missed in the next coming weeks since he starts a three-match ban on Monday after head-butting an opponent at Grenoble last weekend.
Brazilian Brandao scored his first goal for Marseille since joining them from Shakhtar Donetsk in January to give them a 1-0 win at Caen.
Morocco striker Marouane Chamakh found the back of the net four minutes into the second half from close range to earn Bordeaux a 1-0 home win over Lorient.
At the other end of the standings, St Etienne remained in the drop zone after conceding a 2-2 draw at Monaco, who were saved by a stoppage-time equaliser by Yohan Mollo.
