Guilherme Xavier de Sousa (1818-1870) was a Brazilian Marshal and politician who participated in the Paraguayan War as well as other conflicts.

[2] His military career began on November 20, 1834, when he was seated as a soldier, and as a 2nd class Cadet on December 17, 1834.

In 1867 he was promoted to field marshal the province of Rio Grande do Sul, and in 1868 the Minister of War, the Baron of Muritiba, ordered him to embark for Paraguay to replace the Marquis of Caxias in the Command of the Brazilian forces.

Guilherme was also an abolitionist at a time when the struggle to end slavery hadn't yet been abolished in Brazil.

[4] Guilherme Xavier returned from Paraguay on May 18, 1869, already ill, and died on December 21, 1870, in the city of Desterro at the age of 52.