Buenos Aires is a canton in the Puntarenas province of Costa Rica.

A law of 26 June 1914, created a canton by the name of "De Osa".

This new entity encompassed much of the national territory of southernmost Costa Rica.

Buenos Aires was created on 29 July 1940 by decree 185, segregated from "De Osa".

[2] The canton includes a portion of the Cordillera de Talamanca along its northeastern border.