María Fabiana Ríos (born March 31, 1964, in Rosario, Santa Fe) is an Argentine politician and founder of the Patagonian Social Party.

She moved to Tierra del Fuego, a scarcely populated province on the southern end of Argentina, at the age of 23, and married Gustavo Longui, with whom she had two daughters.

Ríos entered politics under the mentorship of the Socialist legislator Alfredo Bravo, and started working within the Alliance for Work, Justice and Education (the short-lived coalition that brought Fernando de la Rúa to the presidency in 1999).

Upon the breakup of the Alliance after the 2001 crisis, Ríos aligned with Elisa Carrió and worked on the construction of the local ARI.

[3] Later that year, she was elected National Deputy for Tierra del Fuego, defeating the Justicialist Party and obtaining the first electoral victory for the nascent ARI at the provincial level.