8:10 AM PT -- A source close to Madonna says doors were at 7:30 PM, her opener, DJ Honey Dijon went on at 8:30 and then Madonna was scheduled to hit the stage between 9:30 and 10.

Our source says there were issues with the audio, so it further delayed Madonna's start time ... she eventually hit the stage around 10:45 and gave a full show.

Madonna was more than fashionably late to kick off the North American portion of her world tour ... and frustrated fans were quick to unload on the "Material Girl."

The singer was scheduled to start her Barclays Center show in Brooklyn Wednesday night at 8:30 PM -- the first U.S. stop of her "Celebration" tour -- but as the clock ticked past to 10:30 PM, fans started getting restless in their seats, and started ripping Madge on social media.

One person shared a view from their seats, with everyone impatiently waiting for the show to begin ... and another tweeted, "I don't give a f*** if you're Madonna, if you're 3 hours late, you're just f***ing rude."

Another angry fan claimed the whole crowd started chanting "bulls***" as the hours kept going by ... with a separate person writing, "I WANT A REFUND NOW."

Around 11, Madonna ended up starting the show ... and tardiness aside, she still put on a helluva performance with her huge catalog of hits -- and it looked like the crowd was having a blast as the late night went on.

BTW, a source close to Madonna confirms to TMZ that the delay was due to sound issues ... and we're told claims she was 3 hours late are impossible.

Still, 2.5 hours late was enough for fans to express themselves!