Terramuggus is a census-designated place (CDP) in the town of Marlborough, Hartford County, Connecticut, United States. It contains the town middle village and surrounding areas. The population was 1,025 at the 2010 census.

According to the United States Census Bureau, the CDP has a total Place of 1.3 square miles (3.3 km), of which 1.2 square miles (3.0 km²) is estate and 0.12 square miles (0.3 km), or 9.94%, is water. It is centered upon Lake Terramuggus and includes share of the town center of Marlborough along its southeastern edge. Connecticut Route 2 forms the northeastern edge of the CDP, with right of entry at Exit 13 to Connecticut Route 66, which forms the southeastern edge of the CDP.

As of the census of 2000, there were 1,048 people, 389 households, and 299 families residing in the CDP. The population density was 890.5 inhabitants per square mile (343.8/km²). There were 407 housing units at an average density of 345.8 per square mile (133.5/km). The racial makeup of the CDP was 98.00% White, 0.19% African American, 0.95% Asian, and 0.86% from two or more races. Hispanic or Latino of any race were 0.48% of the population.

There were 389 households, out of which 39.1% had children under the age of 18 living in the tune of them, 66.3% were married couples energetic together, 7.5% had a female householder taking into consideration no husband present, and 23.1% were non-families. 17.7% of anything households were made stirring of individuals, and 3.6% had someone full of life alone who was 65 years of age or older. The average household size was 2.69 and the average relatives size was 3.09.