Mariano Fiallos Oyanguren

Mariano Fiallos Oyanguren (28 June 1933 – 25 June 2014) was a Nicaraguan judge and academic. He was rector of National Autonomous University of Nicaragua at León (UNAN-León) from 1974 to 1980 and President of the Supreme Electoral Council from 1984 to 1996, overseeing the country's first democratic transfer of power in 1990.

Biography Mariano Fiallos Oyanguren was born on 28 June 1933, in León, Nicaragua. Fiallos's father was and his mother Soledad Oyanguren. He had four siblings, including writer . Fiallos Gil was a longtime university autonomy advocate and National Autonomous University of Nicaragua at León (UNAN-León) rector from 1957 to 1964, National Guard troops were not allowed physical access to the campus, including to enroll as students. Fiallos played a pivotal role in upholding the integrity of the 1990 election: when he was instructed to announce, at 7PM on election night, 25 February, the results of the first four precincts as victories for the FSLN, he instead chose to read the real results, in which the precincts were split, with two going to the FSLN and two to the ONU candidate Chamorro, who went on to win the election. Antonio Lacayo, a Sandinista supporter who voted for Ortega but ultimately served as a central figure in the Chamorro administration, said later: "Without Mariano Fiallos [Oyanguren] there would have been no democratic transition in 1990."

Fiallos resigned from the CSE in 1996, in response to the 1995 constitutional and electoral reforms, in which the National Assembly had established that members of political parties would make up the departmental and municipal electoral councils and the Voting Receiving Boards. Fiallos said the consequence was that it was no longer possible for the CSE to exercise control.

Fiallos died on 25 June 2014 in León, Nicaragua. He is buried in León.