He's usually known for his cutting wit, but US talk show host Jimmy Kimmel has choked up on air as he condemned the death of Cecil the lion in Zimbabwe.

The comedian was on the brink of tears as he discussed on his late-night talk show, Jimmy Kimmel Live!, how US dentist Walter Palmer had killed the animal on a hunting trip in early July.

Kimmel at first denounced the actions of the dentist, who has closed his dental practice in Minnesota and gone into hiding since it was revealed he paid $US50,000 ($68,000) to kill the lion, one of the oldest and most famous in Zimbabwe.

"The big question is: why are you shooting a lion in the first place? I mean I'm honestly curious to know why a human being would feel compelled to do that? How is that fun?" Kimmel began.

"I'm not against hunting if you're hunting to eat, or to help keep the animal population healthy, or it's part of your culture or something. That's one thing.

"But if you're some a-hole dentist who wants a lion's head over the fireplace in his man cave so his douchebag buddies can gather around it and drink scotch and tell him how awesome he is, that's just vomitus."

Cecil had been fitted with a GPS collar so scientists from Oxford University could study his movements.

As Kimmel urged people to donate to a charity to help those researchers, he had to pause to regain his composure.

"If you want to make this into a positive, you can...," Kimmel trailed off, his voice wavering.

"Ah ... sorry ... I um .. OK. OK. Make a donation, support them.

"At the very least, maybe we can show the world that not all Americans are like this jackhole, here, this dentist."​