Kalasuri Ratnadurai Sivagurunathan was a (7 October 1931 – 9 August 2003) Sri Lankan journalist, lawyer, academic and editor of Thinakaran.

[2] Sivagurunathan joined the Thinakaran in 1955 and worked as a reporter, sub-editor and lobby correspondent.

[1] Sivagurunathan obtained a MA degree from the University of Jaffna whilst working as a journalist.

[1][2][3] He was president of Working Journalists Association of Sri Lanka and a member of the Press Council.

[1][2][3] Sivagurunathan was president of Colombo Tamil Sangam and was awarded the Kalasuri title, a Sri Lankan national honour, for his services to journalism.