Siyyid `Alí Muḥammad Shírází (October 20, 1819 – July 9, 1850) is the founder of Bábism, and one of three central figures of the Bahá'í Faith.

He is a merchant from Shíráz, Persia, who at the age of twenty-four (on May 23, 1844) symbolically claims to be the promised Qá'im (or Mahdi).

After his declaration, he takes the title of Báb, meaning "Gate".

He composes hundreds of letters and books (often termed tablets) in which he states his messianic claims and defines his teachings, which constitute a new sharí'ah or religious law.

His movement eventually acquires tens of thousands of supporters, is opposed by Iran's Shi'a clergy, and is suppressed by the Iranian government, leading to the persecution and killing of thousands of his followers, called Bábís.

In 1850, at the age of thirty, the Báb is shot by a firing squad in Tabríz.

Bahá'ís claim that the Báb was also the spiritual return of Elijah and John the Baptist, that he was the "Ushídar-Máh" referred to in the Zoroastrian scriptures, and that he was the forerunner of their own religion.

Bahá'u'lláh, the founder of the Bahá'í Faith, was a follower of the Báb and claimed to be the fulfillment of his promise that God would send another messenger.