Ānanda (Pali and Sanskrit: आनन्द; 5th–4th century BCE) was the primary attendant of the Buddha and one of his ten principal disciples. Among the Buddha's many disciples, Ānanda stood out for having the best memory. Most of the texts of the early Buddhist Sutta-Piṭaka (Pali: सुत्त पिटक; Sanskrit: सूत्र-पिटक, Sūtra-Piṭaka) are attributed to his recollection of the Buddha's teachings during the First Buddhist Council. For that reason, he is known as the Treasurer of the Dhamma, with Dhamma (Sanskrit: धर्म, dharma) referring to the Buddha's teaching. In Early Buddhist Texts, Ānanda was the first cousin of the Buddha. Although the early texts do not agree on many parts of Ānanda's early life, they do agree that Ānanda was ordained as a monk and that Puṇṇa Mantānīputta (Sanskrit: पूर्ण मैत्रायणीपुत्र, Pūrṇa Maitrāyaṇīputra) became his teacher. Twenty years in the Buddha's ministry, Ānanda became the attendant of the Buddha, when the Buddha selected him for this task. Ānanda performed his duties with great devotion and care, and acted as an intermediary between the Buddha and the laypeople, as well as the saṅgha (Sanskrit: संघ, romanized: saṃgha, lit. 'monastic community'). He accompanied the Buddha for the rest of his life, acting not only as an assistant, but also a secretary and a mouthpiece.

Scholars are skeptical about the historicity of many events in Ānanda's life, especially the First Council, and consensus about this has yet to be established. A traditional account can be drawn from early texts, commentaries, and post-canonical chronicles. Ānanda had an important role in establishing the order of bhikkhunīs (Sanskrit: भिक्षुणी, romanized: bhikṣuṇī, lit. 'female mendicant'), when he requested the Buddha on behalf of the latter's foster-mother Mahāpajāpati Gotamī (Sanskrit: महाप्रजापती गौतमी, Mahāprajāpatī Gautamī) to allow her to be ordained. Ānanda also accompanied the Buddha in the last year of his life, and therefore was witness to many tenets and principles that the Buddha conveyed before his death, including the well-known principle that the Buddhist community should take his teaching and discipline as their refuge, and that he would not appoint a new leader. The final period of the Buddha's life also shows that Ānanda was very much attached to the Buddha's person, and he saw the Buddha's passing with great sorrow.

Shortly after the Buddha's death, the First Council was convened, and Ānanda managed to attain enlightenment just before the council started, which was a requirement. He had a historical role during the council as the living memory of the Buddha, reciting many of the Buddha's discourses and checking them for accuracy. During the same council, however, he was chastised by Mahākassapa (Sanskrit: महाकाश्यप, Mahākāśyapa) and the rest of the saṅgha for allowing women to be ordained and failing to understand or respect the Buddha at several crucial moments. Ānanda continued to teach until the end of his life, passing on his spiritual heritage to his pupils Sāṇavāsī (Sanskrit: शाणकवासी, Śāṇakavāsī) and Majjhantika (Sanskrit: मध्यान्तिक, Madhyāntika), among others, who later assumed leading roles in the Second and Third Councils. Ānanda died 20 years after the Buddha, and stūpas (monuments) were erected at the river where he died.

Ānanda is one of the most loved figures in Buddhism. He was known for his memory, erudition and compassion, and was often praised by the Buddha for these matters. He functioned as a foil to the Buddha, however, in that he still had worldly attachments and was not yet enlightened, as opposed to the Buddha. In the Sanskrit textual traditions, Ānanda is considered the patriarch of the Dhamma who stood in a spiritual lineage, receiving the teaching from Mahākassapa and passing them on to his own pupils. Ānanda has been honored by bhikkhunīs since early medieval times for his merits in establishing the nun's order. In recent times, the composer Richard Wagner and Indian poet Rabindranath Tagore were inspired by stories about Ānanda in their work.