A sage, son of Vibhandaka and a deer, that’s why he was born with horns.
Married with Dasharatha’s daughter Shanta. He did the Putrakamyeshti for Dasharatha.
Read about Rishyasringa here
http://hindumythologyforgennext.blogspot.com/2012/04/sage-rishyasringa-part-1.html