António Maria de Azevedo Machado Santos GCTE GOA (10 January 1875 – 19 October 1921) was a Portuguese Navy officer, remembered as the "Hero of the Rotunda" for his role in the 5 October 1910 revolution.

He left a personal account of the revolution, titled A Revolução Portuguesa: Relatório de Machado Santos ("The Portuguese Revolution: A Report by Machado Santos", published in 1911), one of the most complete accounts of the preparation of the revolutionary movement.

He established the Reformist Party and took part in the failed military coup of 27 April 1913 that aimed to topple Afonso Costa's government, and later, in 1915, supported General Pimenta de Castro's government.

[2] In 1919, he helped suppress a monarchist counter-revolution in the north of the country;[2] he was made a Grand Officer of the Order of Aviz on 11 March of that year, by President João do Canto e Castro.

[2] He was posthumously decorated with the Grand Cross of the Order of the Tower and Sword, in 1926.