PSG were five-time defending champions when they were beaten by eventual runners up Guingamp in the quarters last season, but Thomas Tuchel's side had little trouble in progressing to their first final of the season on Wednesday.
Having had to wait until late on in their scrappy Coupe de France win over Lorient on Sunday, PSG had things far easier from the off thanks to Marquinhos' early header.
Ghislain Konan's own goal doubled PSG's tally, with Marshall Munetsi's red card reducing Reims to 10 men before substitute Nianzou Kouassi bundled in the capital club's landmark competitive goal to wrap up the win in style.
Having made a vital last-ditch block as PSG withstood some early pressure, Marquinhos made his mark at the other end in the ninth minute, rising highest to head home Neymar's cross.
Kylian Mbappe wanted a penalty moments later, though referee Mikael Lesage rightly judged Reims goalkeeper Predrag Rajkovic to have made no contact.
PSG had their second just after the half hour – the unfortunate Konan only able to divert Neymar's brilliant free-kick into his own side's net.
Chasing a club record, Neymar curled wide from the edge of the box on the hour, though Keylor Navas had to keep out Boulaye Dia's effort soon after, with PSG then losing Marquinhos to injury.
Reims' task was made tougher when Munetsi was sent off for a lunge on Marco Verratti, however, and it was Marquinhos' replacement Kouassi who was on hand to deal the final blow from close range after Rajkovic repelled Leandro Paredes' volley.
With tempers boiling over, Rajkovic was fortunate not to join Munetsi in seeing red when he lashed out at Mbappe as PSG cruised into the final.
What does it mean? Last Coupe de la Ligue final sees heavyweights meet
April's final will be the last of the Coupe de la Ligue, with the competition having been scrapped ahead of next season.
PSG v Lyon should prove to be a fitting finale, though – the capital club have won the tournament a record eight times, while seven-time Ligue 1 champions Lyon are looking for just their second Coupe de la Ligue title, having previously triumphed in 2000-01.
Captain Marquinhos leads by example
Marquinhos has been struggling with an injury in recent weeks, but returned to PSG's line-up as skipper at Stade Auguste-Delaune and put in an imperious display at the back, capping it off with a fine header for the visitors' opener at the other end. However, his night was marred by an injury, which forced him off midway through the second half.
No record for Neymar
Having scored in eight successive appearances, Neymar was on the verge of setting a new club record for a longest scoring streak. Despite playing a key part in both of PSG's first-half goals, the forward was unable to find the net himself as the chance to put his name into the PSG record books went begging.
Both sides return to Ligue 1 action at the weekend, with PSG travelling to Lille on Sunday, a day after Reims host Metz.