Hynes Bay, also known as Mosquito Bay, is in the San Antonio Bay in eastern Refugio County

During the Spanish Texas era it was known as Lago de San José and later as Mosquito Bay.

Its current name is from that of Peter Hynes and his son John, members of the Power and Hewetson colony, whose land grants were adjacent to the bay. The Guadalupe River delta two miles above Hynes Bay had been a favorite campground for the Karankawa Indians. In 1852, however, a Texan militia company drove them from Refugio County after an engagement that came to be called the battle of Hynes Bay. Though the bay gradually filled with mud until it was too shallow to be navigable by larger craft, from the 1830s to 1877 small boats and lighters were able to navigate it, bringing supplies to the old settlement of Hynesville. In 1914 Preston R. Austwell, ambitious to make his new town of Austwell a port city, had a channel dredged through the bay, but the channel filled rapidly and was ultimately abandoned. The flat to rolling prairie around the bay is spotted with water-tolerant hardwoods, conifers, and numerous grasses. The area provides habitat for many species of waterfowl and fur-bearing mammals.