Konattu Madam Chidambara Iyer Subrahmania Iyer, known better as K. C. S. Mani (2 March 1922 - 20 September 1987), was a socialist activist of Kerala who is known for his attempt of assassination on C. P. Ramaswamy Iyer, the then Diwan of Travancore, a princely state in India. This incident was a turning point in the history of Kerala, forcing the Diwan to leave Travancore and flee to Madras after assenting to merge Travancore with the Union of India.