The Buffalo Bills might have ended their season in defeat, but they hung out with a big winner on Monday ... hitting the golf course with President Donald Trump!!

Spencer Brown, Dalton Kincaid, Ryan Van Demark, Tommy Doyle and Sam Martin were spotted hanging out with the POTUS at the Trump International Golf Club Palm Beach ... which had to be pretty special, considering it was Presidents' Day.

Brown -- an offensive tackle who signed a four-year extension last year -- shared a group photo of the crew on his Instagram ... and it looked like a great time was had by all.

"45-47," Brown wrote in the caption.

Doyle was hyped about meeting Trump ... and made sure to show his support by wearing a "Make American Great Again" hat.

"Met the president on Presidents Day," Doyle said on his own story ... which also included some American flag emojis.

Trump predicted the Kansas City Chiefs -- the team that beat the Bills in the AFC Championship -- would win Super Bowl LIX ... which, of course, didn't happen ... as the Philadelphia Eagles took home the title.

Trump's been spending plenty of time on the course ... as he was also spotted golfing with Tiger Woods recently.

Perhaps Trump's winning ways will rub off on the Bills ... as they've never hoisted the Lombardi Trophy.