The Curse of the Bambino was a superstition associated with which American sport?

There seems to be many curses, omens, and conspiracies around sports including the infamous Billy Goat curse of the Chicago Cubs, when "Billy Goat" tavern owner, William Sianis was asked to leave during the 4th game of the 1945 world Series at Wrigley field with his pet goat, Murphy. Sianis declared that, "Them Cubs, they ain't gonna win no more!" The "curse" lasted 71 years, until after Sianis died.