The Víctor M. Blanco Telescope, also known as the Blanco 4m, is a 4-metre aperture telescope located at the Cerro Tololo Inter-American Observatory, Chile. Commissioned in 1974 and completed in 1976, the telescope is identical to the Mayall 4m telescope located on Kitt Peak. In 1995 it was dedicated and named in honour of Puerto Rican astronomer Víctor Manuel Blanco.It was the largest optical telescope in the Southern hemisphere from 1976 until 1998, when the first 8-metre telescope of the ESO Very Large Telescope opened.