Here's the deal ... a message popping up on Ticketmaster is claiming Madonna's upcoming shows in Boston are postponed, and now her fans are freaking out.

However, a rep for Madonna tells TMZ ... the shows are not postponed or canceled and she'll be in Boston Jan. 8-9 for her two scheduled shows at TD Garden.

It's unclear why Ticketmaster is giving a pop-up notice that reads, "The Event Organizer has had to postpone your event." We reached out to Ticketmaster ... so far no word back.

As we reported, Madonna announced "The Celebration Tour" back in January 2023 ... it covers her long discography -- spanning over 4 decades.

The 35-city megatour was set to begin in July, but had been postponed for several months in June after Madonna fell ill with a terrible bacterial infection ... something she later revealed put her in a coma for 2 days.

Madonna's been touring since October ... and there have already been a few highlights... like when she gave Santa Claus a holiday lap dance at last week's show in D.C. -- and the man with the bag, aka Jerry Wise, took a rough tumble while on stage. Saint Nick let us know he's doing just fine after the spill.