Sian Ka’an is located between the coordinates 19º 05 ‘- 20º 07’ of north latitude, and 87º 22 ‘- 88º 02’ of west longitude. It occupies an area of 528 thousand 147 hectares, which belong to the Quintana Roo municipalities of Felipe Carrillo Puerto and Tulum. The ejidos that border the biosphere are Pino Suárez, Chunyaxché, Felipe Carrillo Puerto, X-Hazil Sur and Andrés Quintana Roo.
A very peculiar ecosystem in the wetlands of Sian Ka’an is that of the so-called petenes, a masses of trees that can measure up to thirty meters high and that rise among the grass of the marshes. These plant formations are almost unique in the world, because outside the Yucatan peninsula, they exist only in the US state of Florida, where they are known as hammocks, and in Cuba, where they are called cayos de monte.