The defending champions produced a superb performance to move eight points clear at the top of the Ligue 1 table following Monaco's shock 2-0 defeat at Saint-Etienne.
Brazilian defender Maxwell opened the scoring for Laurent Blanc's side five minutes into the second half as he slotted home to score against Marseille for the second time this season after finding the net in the 2-1 win in the reverse fixture in October.
PSG were always in control and a fine display was capped off in the 79th minute as Edinson Cavani marked his return from a thigh injury with his 21st goal of the campaign.
Cavani had missed the last five games because of the problem and demonstrated exactly what PSG had been missing when he turned Gregory van der Wiel's cross home with a powerful header to ensure a 'Le Classique' league double for the capital club.
Defeat for Marseille means that they are now six points behind third-place Lille in the race for the final UEFA Champions League place after Salomon Kalou scored a hat-trick to inspire Rene Girard's side to a 3-2 win at bottom club Ajaccio.
Lille went into the game under pressure following Saint-Etienne's surprise victory and fell behind in the first minute when forward Junior Tallo volleyed Ajaccio ahead from Sigamary Diarra’s delivery.
Kalou levelled from the penalty spot after Johan Cavalli handled in the area in the 26th minute and then turned home Jonathan Delaplace's cross to give Lille the lead 12 minutes later.
Tallo netted his second shortly before the interval with an excellent lobbed finish, only for Kalou to restore Lille's advantage with another penalty following Grenddy Perozo's foul on Nolan Roux.
Lille defender Adama Soumaoro was dismissed eight minutes from time for a rash challenge on Dennis Oliech, but it mattered little as the visitors held on.
Elsewhere, sixth-placed Lyon are now seven points behind Lille following a 0-0 draw with Montpellier.
