Cadambathur Tiruvenkatacharlu Rajagopal (September 8, 1903 – April 25, 1978) was an Indian mathematician.

Rajagopal was born in Madras, India. He studied at Presidency College and graduated with an Honours in mathematics in 1925. He was involved in the clerical service and then taught mathematics at Annamalai University. Rajagopal taught mathematics at Madras Christian College from 1931 to 1951. He joined Ramanujan Institute of Mathematics in 1951 and became its head in 1955. He helped the institute to become India's leading mathematics research centre.

Rajagopal did research on sequences, series, summability, and published more than 80 papers in this area generalising and unifying Tauberian theorems. He also did research in other mathematical topics.

Rajagopal also did research in the history of medieval Indian mathematics. He showed that the series for tan^-1x discovered by James Gregory and those for sin x and cos x discovered by Isaac Newton were known to the Hindu mathematicians 150 years earlier. He identified Madhava as the first discoverer of these series.