Santa Monica is a census-designated place (CDP) in Willacy County, Texas, United States.

According to the United States Census Bureau in 2000, the CDP has a total area of 0.3 square mile (0.9 km2), all land.

20.0% of all households were made up of individuals, and 13.3% had someone living alone who was 65 years of age or older.

There were 30.8% of families and 35.4% of the population living below the poverty line, including 83.3% of under eighteens and none of those over 64.

Santa Monica is served by the Lyford Consolidated Independent School District.