It is indeed called The Lion Sleeps Tonight and has been a hit for The Tokens in 1961, Dave Newman in 1972 and a number one for Tight Fit in 1982. It's heavily based on an old African folk song called Wimoweh, which itself was a hit for Karl Denver in 1961. I wasn't aware it was in The Jungle Book though (I guess you're talking about the live action one, because it certainly wasn't in the original Disney film).