The world's most expensive player returned to South America to deal with a personal issue last week, ruling him out of Wednesday's Coupe de la Ligue victory over Strasbourg.
But the former Barcelona man appeared fresh as he opened the scoring in the fourth minute, before teeing up Kylian Mbappe for the league leaders' second.
Firmin Mubele pulled a goal back for Rennes early in the second half, but the task of completing the turnaround became tougher when captain Benjamin Andre was sent off shortly after the hour mark.
And Neymar's ball over the top played in Edinson Cavani for a delightful chip to make it 3-1 after 75 minutes, before PSG's star man added further gloss with another goal assisted by Mbappe.
2 - Games with at least 1 goal AND 1 assist in the Top 5 European leagues this season:— OptaJean (@OptaJean) 16 December 2017
Kylian Mbappé 5
Leroy Sané 4
An 89th-minute red card for Presnel Kimpembe had little impact on the closing minutes, with Wahbi Khazri clearing the crossbar from the resulting penalty.
The result – PSG's sixth win in a row against Rennes – restores their lead at the top of Ligue 1 to nine points over second-placed Monaco.
Neymar was suspended for last weekend's victory over Lille but took just four minutes to make an impact at Roazhon Park, tapping in from close range after determined work from Mbappe on the right of the box to set up the opportunity.
The visitors were dominating possession and Neymar had an effort deflected just wide of the left-hand post six minutes later, before returning Mbappe's earlier favour with the assist for PSG's second.
The Brazil international was allowed to run in behind Hamari Traore down the left, squaring the ball with the outside of his right boot to set up another simple finish for Mbappe.
There was little by way of an attacking threat from Rennes, who elected to rest in-form forward Khazri for the visit of Unai Emery's side, and Traore was lucky to escape punishment after catching Yuri Berchiche with his studs in an untidy challenge.
Traore was not so fortunate when he desperately brought down the advancing Neymar moments later, picking up the game's first booking, before Morgan Amalfitano fired the hosts' only real chance of the first half wide of the right-hand post.
Edinson Cavani almost made it 3-0 just before the break but Traore was on the line to keep out a delicious flick, and another effort from the Uruguayan was thwarted by goalkeeper Tomas Koubek.
Koubek had to be alert again early in the second period, as a curling Neymar strike drew a diving save from the Czech Republic international, but Rennes halved the deficit eight minutes after the restart.
Amalfitano stooped to head a corner against the post and Mubele was on hand to touch home the rebound after the ball bounced across the face of goal.
That joy was short-lived for the home side, however, as skipper Andre was sent off for two bookings in the space of nine minutes.
Khazri – off the bench in place of Mubele – had substantial penalty claims turned down by referee Antony Gautier in the 67th minute, when he went to ground with more than a helping hand from Kimpembe.
Any lingering hopes of a turnaround were all but ended when Cavani lifted a perfectly weighted chip over Koubek in the 75th minute, and Neymar – sliding in to meet an Mbappe cross – finished the job a minute later.
Kimpembe's reckless high boot earned him a second yellow a minute from time and afforded Rennes one last chance for a consolation goal, but Khazri blasted over from the spot.
Key Opta stats:
- Rennes have lost their last six encounters with Paris in Ligue 1 for the first time. This is their biggest defeat at home against Paris.
- The last three times Rennes have conceded four + goals in a Ligue 1 game have all come versus Paris: 29 April 2016 (0-4), 6 November 2016 (0-4) & today (1-4).
- Paris have scored 55 goals in Ligue 1 2017-18, their highest tally after 18 games. Only Sochaux have done better at this stage in 1935-36 (56).
- Neymar has scored and assisted a goal six times in 13 Ligue 1 games this season (46%). Kylian Mbappe has done so five times (in 14 games), more than any other player from the top five leagues.