Nassau Hall, colloquially known as Old Nassau, is the oldest building at Princeton University in Princeton, Mercer County, New Jersey, United States. In 1783 it served as the United States Capitol building for four months. At the time it was built in 1756, Nassau Hall was the largest building in colonial New Jersey and the largest academic building in the American colonies.

Princeton University is a private Ivy League research university in Princeton, New Jersey. Founded in 1746 in Elizabeth as the College of New Jersey, Princeton is the fourth-oldest institution of higher education in the United States and one of the nine colonial colleges chartered before the American Revolution. The institution moved to Newark in 1747, and then to its current campus, nine years later. It officially became a university in 1896 and was subsequently renamed Princeton University.