Vice-Admiral Syed Mohammad Ahsan HQA, SPk, DSO, (Urdu: ﺴﻴﺩ ﻣﺤﻣﺪ ﺍﺣﺴﻦ) (b. 1921 – d. 1989) was a senior three-star admiral who was the 4th Chief of Naval Staff of Pakistan Navy from October 20, 1966 to August 31, 1969. A naval intelligence officer by profession, Vice-Admiral Ahsan was integral to the establishment and expansion of the capabilities of Naval Intelligence and the elite Naval Special Service Group, and took initiatives to modernize the navy. As director-general of Naval Intelligence, Vice-Admiral S.M. Ahsan participated actively in the war and led the Naval intelligence operations during Indo-Pak 1965 September war.
He was the most trusted companion of President and Chief Martial Law Administrator Field Marshal Ayub Khan and was present at every meeting chaired by Khan. Vice-Admiral Syed Mohammad Ahsan rose to be country's second most influential and powerful man during the Ayub Khan's military dictatorship, playing an influential role in Ayub Khan's military and strategic policies in Pakistan. In 1969, after his tenure as Chief of Naval Staff, Chief Martial Law Administrator General Yahya Khan appointed Vice-Admiral Ahsan as Martial Law Administrator of East Pakistan at the request of the former President.
On 1 September 1969, Vice-Admiral Ahsan assumed the command of East Pakistan as Martial Law Administrator with absolute and authoritative gubernatorial and political power and military power in East Pakistan. Admiral Syed Mohammad Ahsan was the supreme commander of the Pakistan Combatant Forces in the Eastern contingent, and served as the Commander of the Pakistan Eastern Military High Command until his resignation, in protest, on 7 March 1971.