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 Intevention in Mexico, (1862-67) Romero was Benito Juárez's envoy in the United States, and Romero played a key role in keeping the issue of the foreign monarchy in Mexico alive with Abraham Lincoln's government during the American Civil War (1861-65).