Keegan is one of England's top football figures - both as a player and a coach.
It is not clear what form of cancer Keegan is suffering from, but he was reportedly hospitalized recently for stomach pains.
Keegan twice received the Ballon d'Or, the award for the world's best player, in 1978 and 1979. He won several titles during his time as a player at Liverpool, where he made over 300 appearances.
He also played for Hamburger SV and Newcastle.
Keegan has been manager of both Newcastle and Manchester City, and he captained England. As a player, he made 63 international appearances.
