Taylor Swift's Madison Square Garden wedding might still be under wraps ... but Ed Sheeran looks like he may be rehearsing for taking the stage at the nuptials.

One lucky couple got a wedding gift money can't buy ... the "Shape of You" singer and DJ Martin Garrix crashing their reception. Check out the video ... the pair make a surprise entrance before treating the newlyweds and their guests to a live performance of their new song, "Repeat It."

They explained the surprise in an Instagram Reel posted Saturday, saying it started with a DM from a fan asking if they would crash their sister's wedding ... and judging by the reaction, the mission was a success.

The newlyweds and their guests looked completely floored as the two music superstars turned an ordinary reception into a private concert, with phones flying into the air the second the surprise guests walked in.

The timing couldn't be much better, either ... Taylor herself has joked it'd be tough to stop her pal Ed from grabbing a mic at her wedding to Travis Kelce ... and after seeing him crash someone else's big day, it doesn't exactly feel far-fetched.

TMZ previously reported, Stevie Nicks and Tim McGraw are slated to perform at the wedding festivities. Whether Ed will play any role is still unknown ... but this impromptu reception performance certainly won't quiet the speculation.