Toronto Public Library (TPL) is a public library system in Toronto, Ontario. It is the largest public library system in Canada, and in 2023 had averaged a higher circulation per capita than any other public library system internationally, making it the largest neighbourhood-based library system in the world. Within North America, it also had the highest circulation and visitors when compared to other large urban systems. Established as the library of the Mechanics' Institute in 1830, the Toronto Public Library now consists of 100 branch libraries and has over 26 million items in its collection.

The first subscription library service to open in the city was on 9 December 1810, at Elmsley House. During the Burning of York in April 1813, several American officers under Commodore Issac Chauncey's command looted books from the library. Discovering his officers were in possession of the stolen books after they returned to Sackets Harbor, Chauncey ordered the looted books returned to York. The stolen books were returned in two crates, although by the time they arrived, the library had already closed. The books were auctioned off in 1822.

In 1830, a library was established in the York Mechanics' Institute. In 1882, the provincial legislature, under Premier Oliver Mowat, passed The Free Libraries Act, 1882. A public campaign for a free library in Toronto preceded a referendum on the question, held on 1 January 1883, in which Torontonians voted in favour of creating a city library. Alderman John Hallam, whom historian Barbara Myrvold describes as having an "almost idolatrous regard for books", was a principal booster for the new library.

In 1884, the Mechanic's Institute's collection became the Toronto Public Library. James Bain was the first chief librarian and he supplemented the collection with $15,000 worth of books purchased on a trip to England in late 1883.

Between 1907 and 1916, ten libraries were built with funds from the Andrew Carnegie Trust. Several of these Carnegie libraries continue to be used by the public library; one, the original Central Reference Library, is now the Koffler Student Centre at the University of Toronto.

Henry Cummings Campbell was Chief Librarian of the Toronto Public Library from 1956 to 1978, and the first Chief Librarian to hold a professional library degree. He is credited with having contributed to the expansion of the library and its adaptation to an increasingly dynamic and multicultural city.

During the amalgamation of Metropolitan Toronto in 1998, the individual library systems of all the Metro municipalities and of Metro itself were merged into the Toronto system:

This made the Toronto Public Library the largest library system in North America, serving a population of 2.3 million people with 98 branches at the time.