The son of Ashoka traditionally credited with introducing Buddhism to Sri Lanka is Mahinda.
According to Sri Lankan Buddhist chronicles, especially the Dipavamsa and Mahavamsa, Mahinda travelled to the Anuradhapura Kingdom during the third century BCE. He is said to have met King Devanampiya Tissa at Mihintale, near Anuradhapura, and converted the king and others to Buddhism.
The mission is associated with Ashoka’s wider support for Buddhist activity after the Third Buddhist Council. Mahinda’s sister, Sanghamitta, is traditionally credited with bringing a branch of the Bodhi Tree to Sri Lanka and helping establish an order of Buddhist nuns. Together, their missions became central to the island’s Buddhist tradition.
The wording “traditionally credited” matters: Ashoka’s surviving edicts refer to Buddhist missions and Sri Lanka-related activity but do not specifically name Mahinda or Sanghamitta. Some sources also describe Mahinda as Ashoka’s brother rather than son. Nevertheless, in the standard Sri Lankan historical tradition and in a fair trivia setting, Mahinda is the canonical answer.