Heidelberg is a census-designated place (CDP) in Hidalgo County, Texas, United States.

According to the United States Census Bureau, the CDP has a total area of 2.8 square miles (7.3 km2), all land.

There were 423 housing units at an average density of 148.9 per square mile (57.5/km2).

7.3% of all households were made up of individuals, and 4.3% had someone living alone who was 65 years of age or older.

[21] Due to its proximity to the deserts of Chihuahua and Gulf Coastal Plains, Heidelberg's geographic location lies near the boundary of a hot semi-arid climate.

Heidelberg has a wet season concentrated during the late summer and early fall months, peaking in September, when the threat from tropical cyclones is greatest.