BB may stand for:

• Brendan Bayliss of Umphrey's McGee
• Baby in Chinglish
• Barbados (ISO country code)
• Battleship (US Navy hull classification symbol)
• BB - Acronym for Broadband.
• BB demo - An ASCII art based demo program that uses AAlib .
• BB gun (especially the ammunition for it)
• Big Brother, in the novel Nineteen Eighty-Four, or the reality television series of the same name.
• Brigitte Bardot
• Buckingham Branch Railroad (AAR reporting mark BB)
• A bulletin board system in computing
• "Bye bye" in Internet slang
• Big Blind in Texas Hold'em Poker

Bb (B flat) is a musical note.