Sadaiya Nayanar or Sadaiyar is a 7th century Nayanar saint in the Hindu sect of Shaivism, venerated for being father of the prominent saint Sundarar rather than for individual merit. He and his wife Isaignaniyar are generally counted as sixty-second and sixty-third on the list of the sixty-three Nayanar saints. Sundarar is the only Nayanar with both parents venerated.

The Nayanars were a group of 63 Tamil Hindu saints living during the 6th to 8th centuries CE who were devoted to the Hindu god Shiva. Along with the Alvars, their contemporaries who were devoted to Vishnu, they influenced the Bhakti movement in early medieval South India. The names of the Nayanars were first compiled by Sundarar. The list was expanded by Nambiyandar Nambi during his compilation of material by the poets for the Tirumurai collection, and would include Sundarar himself and Sundarar's parents.