The former was unavailable for Wednesday's 3-1 win over Montpellier HSC due to muscular discomfort, which has not subsided in time for the weekend.
During the first half of PSG's contest with Montpellier at the Stade de la Mosson, PSG were dealt a double injury blow, with Kylian Mbappe and Ramos both forced into early withdrawals.
Following Mbappe's exit, Ramos suffered a nasty clash of heads with Stephy Mavididi and came off amid fears of a suspected concussion, leading to further examinations on Thursday.
However, Ramos was also reported to have sustained an injury to his adductor in midweek, and PSG have now confirmed that the 36-year-old has indeed been diagnosed with a groin strain.
Neither man should be in danger of missing PSG's Champions League last-16 opener with Bayern Munich on February 14, though, with a medical update stating that both players should return to team action next week.
"Neymar Jr. is continuing his treatment and individual training sessions following a pain in his groin. He will resume team sessions at the beginning of next week. Sergio Ramos will return to training with the squad at the beginning of next week after suffering a groin strain," the statement read.
Prior to Ramos's substitution against Montpellier, Mbappe had to be taken off with an apparent thigh issue, having stayed down after a tackle from Paillade midfielder Leo Leroy.
PSG manager Christophe Galtier was initially hopeful that Mbappe had not suffered a serious injury, but the 24-year-old has now been ruled out for three weeks, meaning that he will miss the showdown with Bayern in 11 days' time.
With Mbappe and Neymar sidelined, the attacking responsibility will fall onto the shoulders of Lionel Messi, who scored PSG's second goal and his ninth of the Ligue 1 season against Montpellier on Wednesday.
Speaking at his pre-game press conference, Galtier hailed the 35-year-old Argentine for "taking charge" after Ramos and Mbappe had both been taken off at the Stade de la Mosson.
"Leo Messi took charge against Montpellier, as soon as Kylian Mbappe and Sergio Ramos left the field. He was a natural leader and the players got behind him," Galtier told reporters.
"I congratulated everyone for doing the necessary work to get this win, which was difficult to achieve. Neymar Jr and Kylian Mbappe's absence is inevitably a shame as there were many connections between these three players.
"I now have to organise the team taking into account these combined absences. Leo Messi will continue to play in his own area, always in the area where he likes to play. After that, it will also be up to the players next to him to seize the opportunities that there will be and for everyone to raise their level of play."
Hugo Ekitike and Carlos Soler will likely fill in alongside Messi, while Warren Zaire-Emery is also knocking on the door after becoming PSG's youngest-ever goalscorer at the age of 16 years and 330 days against Montpellier.
Nordi Mukiele also remains out with a hamstring problem for PSG, while Marco Verratti is suspended, and Presnel Kimpembe (Achilles) is still absent, despite returning to training earlier this week.
PSG SQUAD:
Donnarumma, Letellier, Rico; Hakimi, Pembele, Marquinhos, Bitshiabu, Pereira, Bernat, Mendes; Ruiz, Sanches, Soler, Zaire-Emery, Vitinha, Gharbi; Messi, Ekitike, Housni