Matías Romero Avendaño (24 February 1837 – 30 December 1898) was a Mexican politician and diplomat who served three times as Secretary of Finance and twice as ambassador of Mexico to the United States during the 19th century.

During the French Invasion of Mexico, Romero played a key role in lobbying the United States to oppose the French-backed Second Mexican Empire.

When Abraham Lincoln and Secretary of State Seward appeared ambivalent on the matter, Romero supported the presidential campaign of John C. Frémont in 1864.

[7] After the restoration of the Mexican Republic, Romero served in the government of Porfirio Díaz and was a proponent of foreign investment in Mexico.

Treaties signed pertain to claims of Mexican citizens against the U.S. and vice versa, citizenship, and consular matters.

He was named ambassador extraordinaire and minister plenipotentiary, and in that capacity he signed a preliminary agreement on borders with Guatemala.