A Carnegie library is a library built with money donated by Scottish-American businessman and philanthropist Andrew Carnegie. A total of 2,509 Carnegie libraries were built between 1883 and 1929, including some belonging to public and university library systems. 1,689 were built in the United States.

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Nearly all of Carnegie's libraries were built according to "the Carnegie formula," which required financial commitments for maintenance and operation from the town that received the donation. Carnegie required public support rather than making endowments because, as he wrote:

"an endowed institution is liable to become the prey of a clique. The public ceases to take interest in it, or, rather, never acquires interest in it. The rule has been violated which requires the recipients to help themselves. Everything has been done for the community instead of its being only helped to help itself."

Carnegie required the elected officials—the local government—to:

• demonstrate the need for a public library;

• provide the building site;

• pay staff and maintain the library;

• draw from public funds to run the library—not use only private donations;

• annually provide ten percent of the cost of the library's construction to support its operation; and,

• provide free service to all.