BAB may refer to:

• Back-arc basin, a geologic feature: a submarine basin associated with island arcs and subduction zones
• "Base Attack Bonus", a term used in d20 System RPG games
• Beale Air Force Base (IATA airport code: BAB) in California
• Biotechnology and Applied Biochemistry, an academic journal
• Boris Berezovsky (businessman), Boris Abramovich Berezovsky, a powerful Russian oligarch in self-imposed exile in London from 2001
• Build America Bonds, a type of municipal bond created by the American Recovery and Reinvestment Act of 2009
• Bunty Aur Babli, a 2005 Indian film
• German autobahns or Bundesautobahn, federal motorways in Germany
• B. A. Baracus, character on 1980s action series The A-Team
• The British Aikido Board, a federation of independent Aikido associations within the United Kingdom
• The stock symbol of Babcock International

Bab can refer to:

• Set (mythology) (also known as Bab, Baba, or Seth) ancient Egyptian God
• Bāb, an Arabic word meaning gateway
• Each of The Four Deputies or Gates, intermediaries between the Hidden Imam and the community in Twelver Shia Islam (873–941)
• Báb (Siyyid `Alí Muḥammad Shírází, 1819–1850), founder of Bábism and a central figure in the Bahá'í Faith
• Bab-ı Âli, the gate to the palace of the Grand vizier of the Ottoman Empire. Also known as the Sublime Porte.
• Báb, Nitra District, a village and municipality in the Nitra District in western central Slovakia
• Bab Ballads, cartoons published by W. S. Gilbert under the childhood nickname, Bab

Siyyid `Alí Muḥammad Shírází (, ; October 20, 1819 – July 9, 1850) was the founder of Bábism, and one of three central figures of the Bahá'í Faith. He was a merchant from Shiraz, Persia who, at the age of twenty-four (on the evening of May 22, 1844), claimed to be an inspired interpreter of the Qur'an within the Shaykhi school of Twelver Shi'ism. He made bolder claims as time passed, and in 1847, during a trial in Tabriz, asserted a claim to be the Shi'i 'promised one' or Qá'im (or Mahdi). After his declaration he took the title of Báb (, ) meaning "Gate" or "Door". He composed numerous letters and books in which he stated his messianic claims and defined his teachings, which constituted a new sharí'ah or religious law. His movement eventually acquired thousands of supporters, was opposed by Iran's Shi'i clergy, and was suppressed by the Iranian government, leading to the persecution and killing of between two and three thousand of his followers, called Bábís. In 1850, at the age of thirty, the Báb was shot by a firing squad in Tabriz.

The abbreviation "Bab." may refer to:

• Charles Cardale Babington, an English botanist
• The Babylonian Talmud