Nagarajan Muthukumar (12 July 1975 – 14 August 2016) was a Tamil poet, lyricist, and author. Best known for his Tamil language film songs, he received the most Filmfare Awards for Best Lyricist in Tamil and was a two-time recipient of the National Film Award for Best Lyrics for his works in Thanga Meenkal (2013) and Saivam (2014).

Muthukumar grew up in Kannikapuram village in Kancheepuram, India in a middle-class family. He has a brother Ramesh Kumar. At the age of six and a half, he lost his mother. At a young age, he acquired an interest in reading. He began his career working under Balu Mahendra for four years. He was later offered to write lyrics in the film Veera Nadai, directed by Seeman. He has been credited as a dialogue writer in a few films, including Kireedam (2007) and Vaaranam Aayiram (2008). His last movie as a lyricist is Sarvam Thaala Mayam with A.R. Rahman.

Na. Muthukumar was born at Kannikapuram, Kancheepuram on 12 July 1975. He did his graduation in Physics at Kancheepuram Pachaippa college. He pursued his master's degree in Tamil at Chennai Pachaippa college. With the aim of becoming a director, he joined as an assistant director to the legendary Balumahendra. His Poem 'Thoor' took him to great heights. On 14 June 2006, he married Jeevalakshmi in Vadapalani, Chennai.

Muthukumar, who had been suffering from jaundice for a long time, died on the morning of 14 August 2016, at his Chennai residence, of cardiac arrest. He is survived by his wife, son and daughter.