Celine Dion: Breakdown in Vegas ... Don't Wanna Be All By Myself

Celine Dion lost it during her Vegas concert -- the first time she's performed since her husband's death.

Celine was performing "All By Myself" when she broke down.

Celine added a tribute to Rene Angelil to her show.

It's tough to watch, but the crowd helps her through it ... it ends on a high note.