Sundararaman Ramanan (born 20 July 1937) is an Indian mathematician who works in the area of algebraic geometry, moduli spaces and Lie groups. He is one of India's leading mathematicians and recognised as an expert in algebraic geometry, especially in the area of moduli problems. He has also worked in differential geometry: his joint paper with MS Narasimhan on universal connections has been influential. It enabled SS Chern and B Simons to introduce what is known as the Chern-Simons invariant, which has proved useful in theoretical physics.