Jon Stewart Breaks Down in Tears Mourning His Dog Dipper on 'Daily Show'

Jon Stewart was an emotional wreck on his comedy show this week -- breaking down over the death of his dog ... with a tribute he could hardly get through without sobbing.

The comedian was playing host again on Monday for the 'Daily Show,' and at one point during his time in the chair -- he took a moment to acknowledge the passing of his longtime pooch, Dipper, who he says recently passed away.

Check it out ... it's incredibly sad to watch, as Jon is pretty inconsolable here in front of an audience -- having to stop his train of thought several times as he chokes up and tears up.

He gives the backstory of how Dipper came into his and his family's life -- explaining that they adopted him from a no-kill shelter in NYC called Animal Haven ... and noting that they had a Brindle pit bull in their ranks who'd been hit by a car and who'd lost one of his legs.

That ended up being Jon's family doggo ... and his remembrance here is poignant and moving. As Jon says himself, "In a world of good boys, he was the best."

Unclear how exactly Dipper died, but it sounds like it might've been due to old age. Jon says the dog was ready, but he wasn't -- and that much is clear by how moving this is.