Darien High School is the single public high school serving the town of Darien, Connecticut, in the United States.

In 2014, Darien High School had the highest SAT scores in the state. In the 2004–2005 school year, Darien had the second highest CAPT score in the state and the highest Advanced Placement scores in the school's history, with a 100 percent pass rate on AP math exams and more than 85 percent of students earning the top score of "5." About one in three students in the school takes an AP math course.

Darien High School was specifically ranked 22nd in the nation for best STEM high school by U.S. News & World Report, a list of the top science, technology, engineering and math schools in the United States.

Of the 200 graduating seniors in June 2017, 13 won national recognition in the National Merit Scholarship Program, with 13 as "merit finalists"  and three as National Merit Scholars.[

For the purpose of comparison with the achievement levels of similar schools, the state Department of Education classifies schools and communities in "District Reference Groups," defined as "districts whose students' families are similar in education, income, occupation and need, and that have roughly similar enrollment." Darien is one of eight school districts in District Reference Group A (the others are Easton, New Canaan, Redding, Ridgefield, Weston, Westport, and Wilton).

The school's sports teams have won numerous state championships. Darien is known for its competitive football, lacrosse, ice hockey, field hockey, volleyball, and track teams.

A tradition at the school's graduation ceremonies is to present honorary diplomas to school teachers or administrators who are retiring. In 2007, they were presented to a school counselor and school librarian.