Pudukkottai Ulaganathan Pillai Chinnappa (5 May 1916 - 23 September 1951), also popularly known as P.U.Chinnappa, was a popular singer and Tamil movie actor during 1930's and 1940s from Pudukottai, Tamil Nadu, India. He is also credited to be one of the first major influential actors of South Cinema. His notable movies include 'Utthama Puthran 1940', ‘Aryamala’ (1941), ‘Kannagi’ (1942), ‘Manonmani’ (1942), ‘Kubera Kusela’ (1943) and ‘Jagathalapradaban’ (1944).

P. Unnikrishnan (born 9 July 1965) (Malayalam:ഉണ്ണികൃഷ്ണൻ) is a Carnatic vocalist and a national award winning playback singer.

Unnikrishnan was born to K. Radhakrishnan and Dr. Harini Radhakrishnan in Palakkad, Kerala. The family home, Kesari Kuteeram, was a well known landmark of Madras city, with great grandfather Dr KN Kesari being an eminent Ayurvedic physician and the promoter of the popular Telugu women's magazine Gruhalakshmi .

He went to Asan Memorial Senior Secondary School, Chennai, in 1983. He graduated from Ramakrishna Mission Vivekananda College, Chennai, and received his B.Com degree from the Madras University. He earned a General Law and Post Graduate Diploma in Personnel Management and Industrial Relations.

He worked as an executive in Parrys Confectionery Ltd. from 1987 to 1992 and quit his job to become a professional singer.

Unnikrishnan was initiated into Carnatic Music at age of 12 by Seshadri, Unnikrishnan. He was inspired by Sangita Kalanidhi Dr. S. Ramanathan. He attended a special workshop for six months on "Veena Dhanammal Bhani" under Sangeetha Kalanidhi T.Brinda and Sangeetha Kalanidhi Dr.T.Vishwanathan.