After a goalless first half in which Jordan Veretout hit the post for Nantes, Origi opened the scoring within a minute of the restart, heading home a cross from Florent Balmont.
Three minutes later, the Belgian international, who was bought by Liverpool in the summer before being loaned back to LOSC, provided the pass for Rony Lopes to apply the finish.
It was a first goal for the Portuguese midfielder since he moved to the Stade Pierre-Mauroy on loan from Manchester City in the summer transfer window.
Rene Girard’s side, who will face the Russians of FC Krasnodar in the Europa League on Thursday, are a point clear of both Bordeaux and Saint-Etienne at the Ligue 1 summit, with champions Paris Saint-Germain a further point adrift in fourth.
A draw will be enough for Bordeaux to reclaim first place when they go to Guingamp later on Sunday afternoon, before Marseille visit Evian in the day’s late kick-off.
Saint-Etienne beat Caen 1-0 on Saturday while champions Paris Saint-Germain drew 1-1 at Rennes, despite Zoumana Camara giving them a first-half lead.
Read more here Capital Sports