Krishnaswamy Subrahmanyam (19 January 1929 – 2 February 2011) was a prominent international strategic affairs analyst, journalist and former Indian civil servant. Considered a proponent of Realpolitik, Subrahmanyam was an influential voice in Indian security affairs for a long time. He was most often referred to as the doyen of India's strategic affairs community, and as the premier ideological champion of India's nuclear deterrent. His son S Jaishankar was appointed India's External Affairs Minister in 2019.

Subrahmanyam was a key figure in framing and influencing Indian security, nuclear policy and in advocating Indian nuclear positions on the global stage, both as a policy wonk and as a journalist. He was the second director of the New Delhi-based Institute for Defence Studies and Analyses. He is also noted for having steered several Indian government committees and commissions of inquiry, including the Kargil Review Committee after the Kargil War. Subrahmanyam was a major advocate of the 2007 Indo-US civilian nuclear agreement, adding some heft to the Manmohan Singh government's championing of the deal in the face of much opposition.

He was afflicted by cancer in his final years, and died of a cardiac arrest at the All India Institute of Medical Sciences in 2011, where he had been hospitalised for lung and cardiac problems.