Sivaraj Ramseshan (10 October 1923 – 29 December 2003) was an Indian scientist known for his work in the field of crystallography.

Ramaseshan is the nephew of Indian scientist and Nobel laureate Sir C. V. Raman and cousin of Subramanyan Chandrasekhar.

[1][2] He had his schooling in Nagpur and started his forays into science as a research student under his uncle, Sir C. V. Raman.

During this time, he developed an interest in X-ray crystallography and was instrumental in improving the material science division in the National Aerospace Laboratories.

He served as the director of IISc from 1981 to 1984, as president of the Indian Academy of Sciences (1983–1985), and honorary distinguished professor emeritus at the Raman Research Institute (1984–2003).