Mariano Barbacid Montalbán (born 4 October 1949 in Madrid)[1] is a Spanish molecular biochemist who discovered the first oncogene HRAS.

He completed his higher education in the Universidad Complutense de Madrid, where he studied chemical sciences, and in the United States, where he started as an intern; years later he was appointed director of the National Cancer Institute.

He then moved back to his native Spain to lead the newly created CNIO (Centro Nacional de Investigaciones Oncológicas).

His discovery was published in Nature in 1982 in an article titled "A point mutation is responsible for the acquisition of transforming properties by the T24 human bladder-carcinoma oncogene".

[2] He spent the following months extending his research, eventually discovering that such oncogene was the mutation of an allele of the Ras subfamily, as well as its activation mechanism.