PSG later host third-placed Marseille (20:00), who are five points adrift, with former England captain David Beckham expected to make his debut at the wealthy capital side.
The 20-year-old Ghezzal tapped in the ball five minutes into the second half as Lyon, who wrapped it up thanks to an Arnold Mvuemba last-gasp goal, recovered from one down to move to 51 points, trailing PSG on goal difference.
"I've waited for this goal for a long time now," winger Ghezzal, who was playing his 12th league game, told French channel beIN Sport.
"I am lucky to score at home and help the team join up with the leaders before tonight's game. It's all good."
Jeremie Aliadiere had headed the visitors in front following a corner kick in the 11th minute, only to see Lisandro Lopez fire past goalkeeper Fabien Audard 13 minutes later to make it 1-1 with his eighth goal of the season.
Lorient could have regained the lead in a entertaining first half but saw Kevin Monnet-Paquet's 27th-minute effort from the left side of the box hit the post.
Lyon went ahead on their first second-half chance when Ghezzal notched up his maiden league goal after Audard had parried a Lisandro header in his path.
The seven-times French champions then controlled the play until former Lorient player Arnold Mvuemba sealed the victory with a powerful strike in the 90th minute.