The most commonly accepted name of Buddhism's oldest existing school. The school's adherents, termed Theravādins, have preserved their version of Gautama Buddha's teaching in the Pāli Canon.

The founder of the Theravada sect of Buddhism was Upali.

Theravada is one of the major branches of Buddhism and is widely practiced in Sri Lanka, Myanmar, Thailand, Laos, and Cambodia. It is the oldest surviving branch of Buddhism and is known for its strict adherence to the original teachings of the Buddha.

1. Upali: The founder of the Theravada sect
Upali was a disciple of the Buddha and played a significant role in the establishment of the Theravada sect. He was born in the city of Kosambi and belonged to the Sudra caste. Upali was initially a follower of the Jains but later converted to Buddhism after meeting the Buddha.

2. Upali's role in the First Buddhist Council
After the passing of the Buddha, the First Buddhist Council was convened to preserve and codify his teachings. Upali played a crucial role in this council as he was appointed as the guardian of the Vinaya Pitaka, the Buddhist scriptures containing rules and regulations for the monastic community. Upali's deep knowledge of the Vinaya made him an authoritative figure in the early Buddhist community.

3. Upali's contribution to the development of Theravada Buddhism
Upali's expertise in the Vinaya and his commitment to preserving the original teachings of the Buddha greatly influenced the development of Theravada Buddhism. He emphasized the importance of strict monastic discipline and adherence to the Vinaya rules. Upali's teachings laid the foundation for the Theravada sect, which became known for its conservative approach and focus on meditation and insight.

4. Influence of Upali's teachings
Upali's teachings and the establishment of the Theravada sect had a lasting impact on Buddhism. The Theravada tradition spread to various parts of Southeast Asia, where it continues to be practiced today. The sect's emphasis on individual effort, meditation, and the pursuit of enlightenment has been influential in shaping the lives of millions of Buddhists.

In conclusion, Upali was the founder of the Theravada sect of Buddhism. His deep knowledge of the Vinaya and his commitment to preserving the original teachings of the Buddha played a significant role in the development and spread of Theravada Buddhism.