Lieutenant-General Lionel Protip "Bogey" Sen DSO (20 October 1910 – 17 September 1981) was a decorated Indian Army general. He served as the Chief of the General Staff during 1959–1961 and commanded the Eastern Command during 1961–1963. He was the general responsible for countering the Chinese invasion of NEFA during the Sino-Indian War of 1962. Sen is also the author of Slender was the Thread, a military history of the Indo-Pakistani War of 1947–1948.