Martín Perfecto de Cos (1800–1 October 1854) was a general for the Mexican army and a politician during the mid-19th century. Born in Veracruz, the son of an attorney, he became an army cadet at the age of 20, a Lieutenant in 1821, and a Brigadier General in 1833.
Cos is perhaps best known as a commander of Mexican forces during the Texas Revolution in the 1830s. In September 1835, he was sent by President-General Antonio López de Santa Anna to investigate the refusal of Texians to pay duties during the Anahuac Disturbances. General Cos dispersed the legislature of Coahuila y Tejas, then in session at Monclova, landed 300 men at Matagorda Bay, established a headquarters in San Antonio, and declared his intention of ending Texian resistance in Mexican rule. He attempted to arrest several Texian critics of Santa Anna, but his demands were resisted; a force of Texians under Stephen F. Austin and Edward Burleson held the Mexican troops for two months in the siege of Béxar until Cos surrendered after an attack led by Benjamin R. Milam in December 1835. Cos and his men were released on their pledge not to oppose further the Constitution of 1824, which Santa Anna had recently repealed.