Al-Marwani (Arabic: ُٱلْمَرْوَنِي, romanized: al-Marwānī) or Banu Marwan (Arabic: بَنِوُ مَرْوَانَ, lit. 'Sons of Marwan'), also referred to as the Marwanids (Arabic: ٱلْمَرْوَنِيُون, romanized: al-Marwāniyūn), is a prominent Arab clan belonging to the Banu Umayya branch of the Quraysh tribe. They are the descendants of Marwan ibn al-Hakam, fourth Umayyad caliph and paternal first cousin of the Rashidun caliph Uthman ibn Affan. Their roots lie in the holy city of Mecca in the Hejaz, the ancestral homeland of the Quraysh tribe, while their historical establishment was in Damascus, Syria. They are considered first cousins of the Banu Hashim, the clan of the Prophet Muhammad, since Umayya ibn Abd Shams ibn Abd Manaf was the paternal nephew of Hashim ibn Abd Manaf. They are also cousins of the Banu Shayba clan of Quraysh, the hereditary custodians of the Kaaba, through Marwan's maternal grandmother al-Sa'ba bint Abi Talha Abd Allah ibn Abd al-Uzza al-Abdariyya, the paternal aunt of Uthman ibn Talha ibn Abd Allah al-Abdari upon whom the Prophet Muhammad entrusted the guardianship of the keys of the Kaaba after the Conquest of Mecca.
The clan arrived in Damascus in the second half of the 7th century CE when Marwan I, the family's progenitor, moved from the Hejaz to Syria. His accession at the tribal conclave of Marj Rahit (684) marked the transfer of the caliphate within the Banu Umayya clan from the family of Abu Sufyan to his family. The family constitutes one of the two principal cadet branches of the Umayyad dynasty, the other being the Sufyanids, descended from Muʿawiya I ibn Abi Sufyan. At their height, the Marwanis represented the dominant branch of the Umayyad family, producing most of its ruling members and remaining the most numerous line of Umayyad descendants in later generations. The family supplied caliphs, princes, governors and commanders in the 7th–11th centuries and continued as a recognizable lineage in the central Islamic lands and in al-Andalus after 750.