Toppur Seethapathy Sadasivan (May 22, 1913 – August 18, 2001) was an Indian plant pathologist, academic and the director of the Centre for Advanced Studies in Botany of the University of Madras. He was the founder of the School of Physiological Plant Pathology at Madras University and was a recipient of the Shanti Swarup Bhatnagar Prize, the highest Indian award in the science category. He was an elected fellow of the Indian Academy of Sciences, Indian National Science Academy and Indian Botanical Society and an elected member of the Academy of Sciences Leopoldina. The Government of India awarded him the third highest civilian honour of the Padma Bhushan, in 1974, for his contributions to science.