Port Alto is an unincorporated community in Calhoun County, Texas, United States.

[1] According to the Handbook of Texas, the community had a population of 45 in 2000.

It is part of the Victoria, Texas Metropolitan Statistical Area.

[2] Port Alto is located at the intersection of Texas State Highway Spur 159 and Farm to Market Road 307 on the western shore of Carancahua Bay, 4 mi (6.4 km) east of Olivia, 22 mi (35 km) southwest of Palacios, and 21 mi (34 km) northwest of Port Lavaca in northeastern Calhoun County.

[3] Port Alto is served by the Calhoun County Independent School District.