Dhanush was born as Prabhu Kasturirajan on 25th February 1984 in Chennai, Tamil Nadu. His father is Kasturirajan, a Tamil film director. His brother Selvaraghavan, is also a director and is married to actress Sonia Aggarwal who was Dhanush's co-star. He has two older sisters.
Dhanush's wife is Aishwarya Rajnikanth, superstar Rajnikanth's wife. They have a son named Yathra.