A Persian word applied to a follower of the Báb, or to the elements of the religion he proclaimed. The proper transliteration of this word, in the system used by Bahá'ís, is Bábí, but in electronic formats the accent marks are often omitted. This term is now used in place of obsolete terms such as "Babist" and "Babism."

The Babi period began in the spring of 1844, when the Báb first began to proclaim his station as the Promised One whose arrival was expected by many of the Shi'ih Muslims in Persia at that time. Baha'is perceive the Babi period as the early phase of their own religious history. In fact, the Baha'i calendar starts from the date of the Báb's first declaration of his mission: May 23, 1844.

The Babi community gradually became known as the Baha'i community after learning that Bahá'u'lláh had declared himself to be the new Manifestation of God foretold by the Báb. The first announcements of this claim (outside of Baha'u'llah's immediate family and closest companions), made in late April or early May of 1863, brought the Babi dispensation to a close.

The news traveled slowly at first due to government persecution of the Babi community. It took years just to inform even the most active core of the community. A few of the Babis resisted the idea at first, but many found the evidence in the Báb's writings to be overwhelmingly in Baha'u'llah's favor. By 1870, almost all of the most active Babis had changed to referring to themselves as Baha'is. Of those who did not accept the new name, the majority eventually drifted back to their previous religious communities.

The proper pronunciation of the word Bábí can be difficult for English speakers to achieve. Many end up saying it like the name "Bobby." This produces vowel sounds that are approximately correct, but the stresses come out wrong. The first syllable should end with the letter b, with an almost imperceptible pause that leaves the "ee" sound of the final syllable on its own. Also, each acute accent mark indicates a rising stress on the marked syllable, as is sometimes used in the final syllable of a question in English. Use this instead of the falling tone produced by the unstressed second syllable of "Bobby." Thus, instead of "BAH-bee" the correct sound is more like "Bahb-EE."