The Seattle Public Library (SPL) is the public library system serving the city of Seattle, Washington. Efforts to start a Seattle library had commenced as early as 1868, with the system eventually being established by the city in 1890. The system currently comprises 27 branches, most of which are named after the neighborhoods in which they are located. The Seattle Public Library also includes Mobile Services and the Central Library, which was designed by Rem Koolhaas and opened in 2004. The Seattle Public Library also founded the Washington Talking Book & Braille Library (WTBBL), which it administered until July 2008.

All but one of Seattle's early purpose-built libraries were Carnegie libraries. Although the central Carnegie library has since been replaced twice, all the purpose-built branches from the early 20th century survive; however, some have undergone significant alterations. Ballard's former Carnegie library has since housed a number of restaurants and antique stores among other enterprises, while others such as the Fremont and Green Lake branches have been modernized and remain in use as libraries.

As of 2023, the library served 293,000 active patrons, 75,000 new cardholders, 124,000 borrowers of physical materials, and 175,000 borrowers of digital materials. The library answered 234,000 assisted information questions, and it hosted 3,500 classes, events and activities, as well as 341,000 public computer sessions.

The Seattle Public Library system consists of 27 branches including the Central Library; it also provides a mobile library system.

As of 2023, the Seattle Public Library contained 1.8 million physical items, with 1 million at the Central Library and 814,000 catalogued at the other 26 branches. The total physical collection includes 4.7 million printed books and other printed items; 1.2 million CDs, DVDs, and audiobooks; and 42,000 other items, including laptops, tablets, Wi-Fi hotspots, and Kill A Watt power meters.

As of 2011, its special collections include an oral history collection, the state document depository, the federal document depository, an aviation history collection, genealogy records, and historical documents about Seattle. A room on the seventh floor of the Central Library houses the ZAPP Zine Collection, over 30,000 zines donated by Richard Hugo House, where it used to constitute the Zine Archive and Publishing Project collection. In addition all locations have uncatalogued collections of books that can be borrowed without a library card.^{[citation needed]}

The library also has extensive online resources, which as of 2023 include, among other things, access to historic archives of The Seattle Times, the Seattle Post-Intelligencer, Seattle Daily Journal of Commerce, and The New York Times, as well as the Britannica Library, Kanopy (video streaming), and ProQuest (academic research), plus access to several e-book collections. In 2023, the library circulated 7.4 million digital items, including 5.5 million e-book and e-audiobooks. Through Books Unbanned, these online resources are available to youth ages 13 to 21 throughout the United States. SPL also offers free admission to 13 local museums, zoos, and other attractions that are reserved online.

Seattle's first attempt to start a library association occurred at a meeting of 50 residents on July 30, 1868, but produced only minimal success over the next two decades. The Ladies' Library Association began a more focused attempt to put together a public library in 1888. They had raised some funds and had even obtained a pledge of land from Henry Yesler, but their efforts were cut short by the Great Seattle Fire of 1889. Nonetheless, encouraged by their ideas, the revised October 1890 city charter formally established the Public Library as a branch of the city government. The ladies' influence can be seen in that the charter required that at least two of the five library commissioners be women. The library was funded by a 10% share of city fines, penalties, and licenses.