The Loomis Chaffee School (; LC or Loomis) is an independent, coeducational, college preparatory school for boarding and day students in grades 9–12, including postgraduate students, located in Windsor, Connecticut, seven miles north of Hartford. As of the 2024–2025 school year, 70 percent of Loomis Chaffee's 742 students reside on the school's 300-acre (120 ha) campus and represent 51 foreign countries and 27 U.S. states; the remaining 30 percent are day students.

Founded in 1914, Loomis Chaffee is a member of the Ten Schools Admission Organization.