I Want You (She's So Heavy)" is the last song all four Beatles recorded together.

Yes. They laid down the final takes on August 20, 1969, at Abbey Road. That was the last time John, Paul, George, and Ringo were in the studio together.

You might think it’s “The End” from the same album, but that was recorded a month earlier. “I Want You” was the real goodbye. The song is seven and a half minutes of heavy, repetitive blues, and it ends abruptly—fittingly, with a sudden cut that producer George Martin called “the most dramatic edit we ever made.”

They never recorded all four together again. The 1970 sessions for Let It Be were mostly overdubs and mixing, and the band was already falling apart. So if you want the last honest moment of the Beatles as a working unit, put on “I Want You (She’s So Heavy)” and crank it.