Arulnithi Tamilarasu (born 21 July 1987) is an Indian actor best known for playing the lead role in Vamsam, directed by Pandiraj.

Personal life
Arulnithi's grandfather is M. Karunanidhi, former Chief Minister of Tamil Nadu. His father is M. K. Tamilarasu, brother of M. K. Stalin,Chief Minister of Tamil Nadu. His cousins include noted producers, Udhayanidhi Stalin and Dhayanidhi Alagiri.

Arulnithi was educated at St. Michael's Academy in Chennai, before pursuing a degree at Loyola College. He then went on to Pondicherry University to undertake more qualifications. Arulnithi married Keerthana on 7 June 2015. Their first child, a son, was born in 2017.  Their second child, a girl, was born in November 2021.