The Fugees came together this weekend duringLauryn Hill's headlining set in Philadelphia ... and it might be the last time we see them as a unit for a good long while.

The 3 ex-band members reunited Saturday during the Roots Picnic music festival ... where she was one of the last acts of the night to take the stage. It was a big deal, as she's celebrating the 25th anniversary of her album, "The Miseducation of Lauryn Hill."

It seemsWyclef Jean andPras realized the significance as well ... 'cause at one point during her performance, they joined her onstage and began performing as The Fugees again.

Indeed ... it was a very cool moment. They performed at least one song of theirs -- "Ready or Not" -- and the crowd was rocking with them. It's unclear if they did any other tracks ... but they certainly had plenty to choose from. The Fugees have tons of hits under their belt.

Sounds like the show went off without a hitch, and the festival's key organizer --Questlove-- was certainly grateful. He took toIG with a throwback post of one of The Fugees' first gigs, noting this may well be one of the final times they join forces like this in this setting.

He wrote, "@MsLaurynHill did us a solid by letting us not only letting us celebrate with her the classic #MiseducationOfLaurynHill but she also made a moment by bringing together her bredren @WyclefJean & @PrasMichel ... I’m giving all the gratitude for making this miracle of a night happen."

Part of the reason The Fugees might not reunite like this again for quite some time is because Pras is likely going to prison after he was convicted in his illegal foreign influence scheme case ... and hefaces up to 20 years behind bars. He hasn't been sentenced yet.

Enjoy 'em while you can.