"Crazy Train" is a 1980 heavy metal song written by Ozzy Osbourne, Randy Rhoads and Bob Daisley, released on the album Blizzard Of Ozz.
The theme of the song is dark, but features Ozzy pleading for sanity in what he views as an insane world, hence the chorus "I'm going off the rails on a crazy train."
The song is famous for its opening riff (bolstered by Osbourne's high pitched stacatto scream aieee! aieee! aieee!); one of the most famous in all of heavy metal and rock.