Mayankote Kelath Narayanan (M.K. Narayanan) is the National Security Advisor (NSA) to the Prime Minister of India.

He was appointed to this post on January 25, 2005, three weeks after the former NSA, J N Dixit died on January 3, 2005. He offered to resign on 30 November 2008 over the attacks in Mumbai that killed nearly 200 people, but his resignation was not accepted by the Prime Minister Manmohan Singh. He has been heavily criticized in leading up to the Mumbai terrorists attacks of his preoccupation with Sri Lanka and the LTTE, instead of India's chief threat Kashmir insurgents and Pakistan.

Narayanan headed the Intelligence Bureau (IB) from 1987 to 1990, before heading the Joint Intelligence Committee. He became Chief of the IB again in 1991, before retiring in 1992. He was the Special Advisor for Internal Security to the Prime Minister of India since May 2004.

Narayanan is an expert in security matters and a specialist on Sri Lankan affairs.

He hails from Palakkad, a district of the state Kerala.