Marlborough is a town in Hartford County, Connecticut, United States. It contains the census-designated place (CDP) of Terramuggus. The town is part of the Capitol Planning Region. The town's population was 6,133 at the 2020 census. Marlborough is a suburban and rural community. The local high school is RHAM High School. In 2013, Marlborough ranked third in Connecticut Magazine's biannual ranking of Connecticut small towns. Educationally, RHAM High School, which serves Marlborough, Hebron, and Andover students, is one of the top-ranked regional high schools in the state on the SAT in 2017, and 11th highest-performing school in the state on the test. The town is home to Elmer Theines-Mary Hall elementary school which serves Pre-K through 6th grade. The school scores above state average on standardized testing and student progress.

Hartford County is a county located in the north central part of the U.S. state of Connecticut. According to the 2020 census, the population was 899,498, making it the second-most populous county in Connecticut. Hartford County contains the city of Hartford, the state capital of Connecticut and the county's most populous city, with 121,054 residents at the 2020 census. Hartford County is included in the Hartford-East Hartford-Middletown metropolitan statistical area.