Estero de San Antonio is a stream in the northern California counties of Marin and Sonoma which empties into Bodega Bay.

The Estero de San Antonio has a variety of habitat types, including freshwater ponds, mudflats, eelgrass and saltgrass area, and wooded ravines.

[3] In the summer or early fall, a sandbar often forms at the mouth of the Estero, damming it until the winter rains arrive.

Area residents used to blast the sandbar to dispel high salt concentrations in the Estero.

[2] The United States Geological Survey's Geographic Names Information System cites ten variant names for this stream, including Stemple Creek (the name of its main tributary), Estero De Americano (almost identical to the parallel estuary 2 mi (3 km) north), Arroyo de San Antonio (also applied to Walker Creek, a parallel estuary 5 mi (8 km) south), and San Antonio Creek (the name of a creek further east along the county line).