Sujatha was the pseudonym of the Tamil author S. Rangarajan, author of over 100 novels, 250 short stories, ten books on science, ten stage plays, and a slim volume of poems. He was one of the most popular authors in Tamil literature, and a regular contributor to topical columns in Tamil periodicals such as Ananda Vikatan, Kumudam and Kalki. He had a wide readership, and served for a brief period as the editor of Kumudam, and has also composed screenplays and dialogues for several Tamil movies.

Penning with his wife's name, Sujatha's Tamil literary career spanned more than four decades. An engineer by profession, he was proficient in the language of technology. Widely read and knowledgeable, he presented his knowledge in simple Tamil.

His works stood out during a time when Tamil composing was dominated by social/family dramas and historical novels. His identification with the masses, and his uncanny adoption of their way of talking, behavior, mindset and slang, helped make him popular across multiple demographic segments.

He extended his composing skills and expertise from science to movies. The first of these efforts were Gaayathri and Priya. In Priya, his fictional character Ganesh was played by Rajinikanth. Kamal Hassan's Vikram was composed by him. He penned dialogues for the movie Roja, directed by Maniratnam. In recent times he has been associated with Mani Ratnam (for Kannathil Muthamittal, Aayitha Ezhuthu, etc.), Shankar (for Boys, Anniyan, Indian, Mudhalvan, Sivaji, and Enthiran) and Azhagam Perumal in Udhaya. He was also a co-producer for the banner MediaDreams, which went on to produce the critically acclaimed Bharathi, a biopic of the great Tamil poet Bhaarathiyaar.

He was working on Shankar's Enthiran before he died on 27 February 2008.