La Unión de Isidoro Montes de Oca is a municipality in the Mexican state of Guerrero and is the westernmost municipality in Guerrero.

The municipal seat lies at La Unión.

[2] On October 26, 1614, the Dutch Captain Joris van Spilbergen - involved in his country's war with Spain - raided with an expedition of five ships this part of the coast of the then Spanish Mexico.

At Zacatula he succeeded in capturing the pearl fishing ship San Francisco.

This article about a location in the Mexican state of Guerrero is a stub.