N. Viswanathan (1929 – 17 November 2010), popularly known as Calcutta Viswanathan in the Tamil film industry, was an Indian actor and academic. A Tamilian by birth, he moved to Calcutta (now Kolkata) at a young age and joined St. Xavier's College, Calcutta as an English professor and continued to teach there for more than 40 years. Viswanathan was also a well-known public speaker.