Alejo Bay (1891 in Álamos, Sonora – January 30, 1952) was an Irish Mexican political leader.
His father was Thomas Bay, an Irish-American and Confederate soldier from St. Louis, Missouri, that went to live to Alamos, Sonora after The Union won the war.
Don Alejo Bay figured during a long time in political and federal issues in the Mexican state of Sonora. Alejo Bay was two times federal deputy, senator of the republic, local representative and governor of Sonora during the Constitutional period from 1923 to 1927. He was also the Secretary of Treasury during 1939, under the command of general Macias Valenzuela. He was good friends with President Álvaro Obregón. During 1920, as a senator, he joined a group that was led by generals Jose Gonzalo Escobar and Fausto Topete, against president Plutarco Elias Calles for betraying his comrade Alvaro Obregon which caused him to march in the desert for five years.
Alejo Bay died January 30, 1952 in Rochester, Minnesota, United States.