Clay Pit Pond, also known as Claypit Pond, is a pond in the Boston suburb Belmont in Middlesex County, Massachusetts. It lies between Concord Avenue and Belmont High School. Its waters are notoriously unclean and incidents of students swimming in the pond have resulted in infection. It was used in the past as a source of clay for making bricks. The large pit was flooded with water after operations ceased, leaving some equipment behind.