Donald Trump's joking about the failed attempt on his life as he returns to the scene of the crime ... and he's got Elon Musk with him this time.

The Republican candidate is back in Butler, PA for a rally Saturday ... only 12 weeks after being shot in the ear at the very same podium as the botched assassination attempt.

Trump took the stage from behind bulletproof glass and drew a laugh when he started his speech like this ... "As I was saying." He then pointed to the famous border-crossing chart he said helped save his life back in July when Thomas Matthew Crooks opened fire on him from a nearby rooftop.

DT says the shooter failed to silence him and the MAGA movement ... and folks in the crowd were waving "FIGHT! FIGHT! FIGHT!" signs in a nod to Donald's iconic moment from after the shooting.

Elon, who is endorsing Trump, is in attendance ... as is Trump's running mate, Ohio Senator J.D. Vance.

Trump's on the record saying he's back in Butler to finish his rally ... and the "as I was saying" crack was delivered as only Trump could.

While Trump was only grazed in the ear in the shooting, one person died ... former volunteer fire chief Corey Comperatore. Trump paid tribute to CC at the rally, and Corey's widow, Helen, returned to the venue, along with members of their family.