Upāli (Sanskrit and Pāli) was a monk, one of the ten chief disciples of the Buddha and, according to early Buddhist texts, the person in charge of the reciting and reviewing of monastic discipline (Pāli and Sanskrit: vinaya) on the First Buddhist Council. Upāli belongs to the barber community. He met the Buddha when still a child, and later, when the Sakya princes received ordination, he did so as well. He was ordained before the princes, putting humility before caste. Having been ordained, Upāli learnt both Buddhist doctrine (Pali: Dhamma; Sanskrit: Dharma) and vinaya. His preceptor was Kappitaka. Upāli became known for his mastery and strictness of vinaya and was consulted often about vinaya matters. A notable case he decided was that of the monk Ajjuka, who was accused of partisanship in a conflict about real estate. During the First Council, Upāli received the important role of reciting the vinaya, for which he is mostly known.

Scholars have analyzed Upāli's role and that of other disciples in the early texts, and it has been suggested that his role in the texts was emphasized during a period of compiling that stressed monastic discipline, during which Mahākassapa (Sanskrit: Mahākāśyapa) and Upāli became the most important disciples. Later, Upāli and his pupils became known as vinayadharas (Pāli; 'custodians of the vinaya'), who preserved the monastic discipline after the Buddha's parinibbāna (Sanskrit: parinirvāṇa; passing into final Nirvana). This lineage became an important part of the identity of Ceylonese and Burmese Buddhism. In China, the 7th-century Vinaya school referred to Upāli as their patriarch, and it was believed that one of their founders was a reincarnation of him. The technical conversations about vinaya between the Buddha and Upāli were recorded in the Pāli and Sarvāstivāda traditions and have been suggested as an important subject of study for modern-day ethics in American Buddhism.

Upāli's personality is not depicted extensively in the texts, as the texts mostly emphasize his stereotypical qualities as an expert in monastic discipline, especially so in the Pāli texts.

According to the texts, Upāli was a barber, a despised profession in ancient India. He was from an artisan class family in service to the Sakya princes in Kapilavatthu (Sanskrit: Śakya; Kapilavastu) and, according to the Mahāvastu, to the Buddha. Upāli's mother had once introduced Upāli to the Buddha. The Mahāvastu, Dharmaguptaka and Chinese texts relate that as a child, Upāli shaved the hair of the Buddha. Unlike adults, he had no fear of approaching the Buddha. Once, as he was guided by the Buddha during the shaving, he attained advanced states of meditation. Buddhologist André Bareau argues that this story is ancient, because it precedes the tradition of art depictions of the Buddha with curly hair, and the glorification of Upāli as an adult.

According to the Mahāvastu, the Pāli Cullavagga and the texts of discipline of the Mūlasarvāstivāda order, when the princes left home to become monks, Upāli followed them. Since the princes handed Upāli all their possessions, including jewelry, he worried that returning to Kapilavatthu with these possessions might cause him to be accused of having killed the princes for theft. Upāli therefore decided to become ordained with them. They were ordained by the Buddha at the Anupiyā grove. Several variations on the story of Upāli's ordination exist, but all of them emphasize that his status in the saṅgha (Sanskrit: saṃgha; monastic community) was independent of his caste origin. In the Pāli version, the princes, including Anuruddha (Sanskrit: Aniruddha), voluntarily allowed Upāli to ordain before them in order to give him seniority in order of ordination and abandon their own attachment to class and social status.

In the Tibetan Mūlasarvāstivāda version of the story, co-disciple Sāriputta (Sanskrit: Śāriputra) persuaded Upāli to become ordained when he hesitated because of being lower class, but in the Mahāvastu, it was Upāli's own initiative. The Mahāvastu continues that after all the monks had been ordained, the Buddha requested that the former princes bow for their former barber, which led to consternation among the witnessing king Bimbisāra and advisers, who also bowed for Upāli following their example. It became widely known that the Sakyans had their barber ordained before them to humble their pride, as the Buddha related a Jātaka tale that the king and advisers had bowed for Upāli in a previous life, too.

Indologist T.W. Rhys Davids noted that Upāli was the "striking proof of the reality of the effect produced by Gautama's disregard of the supposed importance of class". Historian H.W. Schumann also raises Upāli as an example of the general rule that "in no case did ... humble origins prevent a monk from becoming prominent in the Order". Religion scholar Jeffrey Samuels points out, though, that the majority of Buddhist monks and nuns during the time of the Buddha, as drawn from several analyses of Buddhist texts, were from higher classes, with a minority of six percent like Upāli being exception to the rule. Historian Sangh Sen Singh argues that Upāli could have been the leader of the saṅgha after the Buddha's parinibbāna instead of Mahākassapa (Sanskrit: parinirvāṇa, Mahākāśyapa). But the fact that he was from humble origins effectively prevented this, as many of the Buddhist devotees at the time might have objected to his leadership position.

Upāli had a dwelling place in Vesāli (Sanskrit: Vaiśāli), called Vālikārāma. He once asked the Buddha for leave to withdraw in the forest and lead a life in solitude. The Buddha refused, however, and told him that such a life was not for everyone. Pāli scholar Gunapala Malalasekera argued that the Buddha wanted Upāli to learn both meditation and Buddhist doctrine, and a life in the forest would have provided him with only the former. The texts state that the Buddha himself taught the vinaya (monastic discipline) to Upāli. Upāli later attained the state of an enlightened disciple.