Mariano Sabino Otero (August 29, 1844 – February 1, 1904) was a Congressional delegate from the Territory of New Mexico, nephew of Miguel Antonio Otero (I) and cousin of Miguel Antonio Otero (II). Born in Peralta, New Mexico, Otero attended private and parochial schools and St. Louis University, Missouri.He engaged in commercial pursuits and stock raising, and subsequently became a banker.He was probate judge of Bernalillo County in 1871–1879.He was also nominated by the Democratic State convention as a candidate for Delegate to the Forty-fourth Congress, but declined.