William Tell (German: Wilhelm Tell, German pronunciation: [ˈvɪlhɛlm ˈtɛl] (listen); French: Guillaume Tell; Italian: Guglielmo Tell; Romansh: Guglielm Tell) is a folk hero of Switzerland. According to the legend, Tell was an expert mountain climber and marksman with a crossbow who assassinated Albrecht Gessler, a tyrannical reeve of the Austrian dukes of the House of Habsburg positioned in Altdorf, in the canton of Uri. Tell's defiance and tyrannicide encouraged the population to open rebellion and a pact against the foreign rulers with neighbouring Schwyz and Unterwalden, marking the foundation of the Swiss Confederacy. Tell was considered the father of the Swiss Confederacy.

Set in the early 14th century (traditional date 1307, during the rule of Albert of Habsburg), the first written records of the legend date to the latter part of the 15th century, when the Swiss Confederacy was gaining military and political influence. Tell is a central figure in Swiss national historiography, along with Arnold von Winkelried, the hero of Sempach (1386). He was important as a symbol during the formative stage of modern Switzerland in the 19th century, known as the period of Restoration and Regeneration, as well as in the wider history of 18th- to 19th-century Europe as a symbol of resistance against aristocratic rule, especially in the Revolutions of 1848 against the House of Habsburg which had ruled Austria for centuries.