ET broke the news Saturday, reporting that the couple split a few weeks ago ... but that the uncoupling was "amicable" and "not dramatic," which isn't always how Taylor Swift breakups go. The outlet goes on to say, citing sources, the relationship had simply run its course.

A sign there was trouble on the horizon, per ET, was the fact Joe hadn't been seen at any of TS's concerts of late. The reason, apparently, is because they'd gone their separate ways. As you know, TayTay is on tour right now -- and Joe has had a habit of coming out to support.

This news is quite the shocker ... Taylor and Joe seemed to be good as recently as this past fall, when they were spotted out in NYC -- not to mention their vacay to the Bahamas last summer where they were packing on the PDA. By most accounts, they were doing great.

JA is usually out of the spotlight, as was their relationship in general. The dynamic between them was, by and large, kept private ... but Taylor seemed head over heels for the guy.

Taylor and Joe first got together back in 2017, so they've been going strong for 6 years now. Up to this point, Joe's been Taylor's most steady and consistent boyfriend since she splashed onto the Hollywood scene ... with a lot of her exes being way more famous.

Remember, she's dated the likes of Jake Gyllenhaal, Harry Styles, Joe Jonas, Tom Hiddleston, Taylor Lautner, Calvin Harris and John Mayer -- to name a few. None went the distance with her the way Joe did ... and many thought they could even get married.

Of course, the other weird thing about this is that Taylor recently put out a new track that was meant to be a love letter to Joe -- although it's unclear when they may have been recorded. In any case, it appears to be sayonara for now for these two ... for now.