Baron of São Cosme (Portuguese: Barão de São Cosme) was a title in the Portuguese nobility created on 12 May 1835 by Queen Maria II of Portugal.
The first holder was João Nepomuceno de Macedo, born in Chamusca (15 May 1793), brigadier general of the liberal constitutionalist army during the Liberal Wars, Knight Commander of the Order of Aviz and of the Order of the Tower and Sword.