The Institute Library is a membership library in New Haven, Connecticut. Founded in 1826 in the tradition of Mechanics' Institutes, it is New Haven's oldest community library and one of the few membership libraries now remaining in North America. The organization was particularly active during the 19th century as a center for lectures, debates, and classes in New Haven.

A subscription library is a library that is financed by private funds either from membership fees or endowments. Unlike a public library, access is often restricted to members, but access rights can also be given to non-members, such as students.