Ra. Ki. Rangarajan (1927 – 18 August 2012), popularly known as Ra Ki (Tamil: ரா.கி.), was a Tamil journalist and prolific author of novels, short stories, essays, translations and other works. Rangarajan wrote under 10 pen names including: Mohini for historical novels, T. Duraisami for family dramas, Surya for youthful romance, Krishnakumar for mysteries, K. Malathi for postal-related stories, Mulri, Vinodh, Hamsa and Avittam for another genres.