Prasanna Puwanarajah (Tamil: பிரசன்னா புவனராஜா; born 1981) is a British actor, director, writer, and former junior medical doctor.

Puwanarajah was born at Ipswich Hospital in Suffolk to Tamil Sri Lankan parents from Sri Lanka, his mother a psychiatrist and his father a dentist. He spent his early childhood on Churchill Avenue in Ipswich before the family moved to Hampshire when he was four. He participated in school plays and spent a season with the National Youth Theatre, but thought of acting as more of a hobby than a career choice at the time.

He trained in Medicine at New College, Oxford. After working as a junior doctor in reconstructive surgery for over three years, Puwanarajah decided to take a year out. It was during this time he decided to become a full-time actor, describing it as "more of a strong pull towards something else" than a "push away from" his medical career.