Rao Sahib Ayyathan Gopalan (3 March 1861 - 2 May 1948), popularly known as "Darsarji"and "Darsar Sahib" ("doctor"), was an Indian physician, writer, philanthropist, and a social reformer. He is the founder of the Sugunavardhini movement and a leader and propagandist of Brahmo Samaj in Kerala. He denounced idol worship and fought to end those social practices in Kerala that he thought were unethical. Among his followers were Brahmananda Swami Sivayogi, Vaghbatananda, and Brahmavadhi P. Kunhiraman. Gopalan titled P. Kunhiraman as "Brahmavadhi" and Sivayogi as "Brahmananda Swami".