Sriman Hiranyagarbha Ravikula Raja Muthu Vijaya Raghunatha Raja Raghunatha Deva Kilavan Setupati (r. 1671–1710) was first Raja of Ramnad. He ruled from 1673 to 1708 and oversaw the growth of the feudal chieftainship of Ramnad into a powerful kingdom. He rescued the Nayak of Madurai from the tyranny of Rustam Khan and also successfully campaigned against the King of Thanjavur, who later ceded all his territories.
He was helpful to Chokkanatha Nayak, a Nayak king who conferred him the title of Para Rajakesari ("lion to alien kings"). He annexed some territories of Madurai Kingdom. Aranthangi, Thirumayam, Piranmalai. He opposed the spread of Christian missionary activities. Kilavan Sethupathi liberated the Marava country from the control of Madurai Nayak. After defeating Rani Mangammal’s army, he declared independent Marava country in 1707. He shifted his headquarters from Pughalur to Ramnad. Kilavan Sethupathi established the Nalcottal palayam (later Sivaganga) and appointed Udaya Thevar as governor. He endowed villages to a temple at Thiruvadanai and Kalaiyar Koil. He constructed a fort around the Ramanathapuram, the capital city. He constructed a dam across the Vaigai.
It was during his reign, that the capital was moved from Pogalur to Ramnad. He was succeeded by his adopted son Vijaya Raghunatha.
He fell in love with Kathali, a girl from the Kallar caste, later married her and then appointed his brother-in-law as the chief of Pudukottai and neighboring districts. He christened him Ragunatha Tondaman in lieu of his former chief Pallavaraya Tondaman whom he had replaced. Ragunatha Tondaman would later go on to spawn the Thondaman Dynasty of Pudukottai. Also, history states that he has many wives(more than 45), and given equal love to all of them. It is one of a rare instance in history that when Kilavan Sethupathi expired, all of them committed sathi "Udankattai."