may have to learn a lesson in punctuality the hard way ... two men just filed a class action against her for starting her concerts late.

According to the docs obtained by TMZ ... Michael Fellows and Jonathan Hadden are leading the charge against the legendary pop star and concert organizer Live Nation claiming they owe big damages after shows scheduled to start at 8:30 PM ET didn't end up starting until 10:30 PM.

According to the lawsuit, the late starts constitute a "wanton exercise in false advertising, negligent misrepresentation, and unfair and deceptive trade practices."

The plaintiffs are suing for unspecified damages and taking aim at all three nights Madonna showed up late to Barclays Center in December -- but they say Madonna has a long-documented history of not starting on time (more on that later).

Another interesting note ... the plaintiffs acknowledge Madonna had a health issue which caused the concert to be pushed from July to December but don't think that's a sufficient excuse for kicking off the actual shows 2 hours late.

These guys also list their pricey tickets ... listing the dollar-amounts at $155.90 and $292.50, respectively. In their mind, that's money down the drain considering how late Madge was.

Remember... a serious bacterial infection put , and sources told us she was for about a month before she finally collapsed. Obviously the tour was ... finally in October.

We knew people were about Madonna's tardiness BTW .

.. when the NYC shows went down back in December, fans took to social media to voice their displeasure at waiting for the Queen of Pop. (FWIW, a source at the time told us the delay was due to sound issues.)

If you think Madonna's sweating the lawsuit, think again ... cause this ain't the first time she's been sued over her late starts!! She was sued back in 2019 and in 2020 for pulling up late to her shows and -- in the case of the 2019 suit -- Madonna gave a G.O.A.T.ed response you gotta hear to believe.