Bill Maher has compared having dinner with President Donald Trump to being one of Taylor Swift's exes ... after the prez launched in an epic tirade against him on social media.

The late-night comedian joked on Friday's "Real Time" ... "I mean, eating with Trump is like dating Taylor Swift. It’s a lot of laughs at the time, but later on, they’re tearing you a new a***hole."

As you may know ... Trump went scorched earth on Bill in his longest Truth Social diatribe yet.

Totaling more than 1,300 words, Trump's rant scathingly labeled Bill a "total loser" with a "low rated show."

Bill also took exception to Trump's characterization that he doesn't agree with the president on removing Iran's nuclear arsenal ... with the comedian playing clips showing him approving of the policy.

Bill also blasted Trump's claims that he calls him "incessantly."

The "Real Time" host fired back ... "I’ve never called you, you call me. I’d be afraid to call you. You’re the president. I think you’re too busy. Well, plainly not."

All in all, Bill calls the rant the "longest ever ... kind of a flex." We'll see if Trump -- or Natalie Harp -- respond with another epic poem.