This is from the opera Gianni Schicchi by Giacomo Puccini. While this is one of my very favorite favorite arias, the opera itself is seldom performed since it is basically a one-act play and too brief for opera goers to feel that they really got their money's worth.
For those who are, like me, really into it, that's soprano Rita Streich actually singing the aria.
· Mr. Bean's Holiday on the IMDB
· Mr. Bean's Holiday (Full Movie) on YouTube
· O Mio Babbino Caro on the Aria Database