Seven-times champions Lyon, who lost their crown to Bordeaux last May, started well, Brazilian midfielder Michel Bastos putting them ahead with a super angled free kick on 22 minutes.
The home side, however, earned a share of the points when Korean forward Park Chu-young volleyed home a Sebastien Puygrenier headed pass 12 minutes later.
Monaco were clearly the better team in the second half, Lyon looking only a pale shadow of the side who ruled France for seven seasons.
Bordeaux, who made sure of ending the year in top spot by crushing Lorient 4-1 on Saturday, head the standings on 40 points from 18 games, followed eight points back by Olympique Marseille, who have a game in hand.
Lille climbed into third, a further point adrift, with a clinical 3-0 win over struggling Le Mans on Sunday.
The home team ignored freezing cold weather to score three times in the first 28 minutes through Aurelien Chedjou, Gervinho and Eden Hazard.
Fourth-placed Lyon are now on 30 points and have done nothing lately to suggest they could challenge Bordeaux, who have clearly taken over as the dominant force in Ligue 1.
There will be one more round of matches on Tuesday and Wednesday before the winter break.
