Some 20 movies, starting with the 1918 silent (with Elmo Lincoln in the title role) and going on to the Johnny Weissmuller/Maureen O'Sullivan classics (the first of which, Tarzan the Ape Man, came out in '32), the 1981 Miles O'Keeffe/Bo Derek remake, Hugh Hudson's 1984 Greystoke: The Legend of Tarzan, Lord of the Apes (with Christopher Lambert and Andie MacDowell), and last year's Tarzan and the Lost City (with Casper Van Dien and Jane March).
Tarzan, most famously incarnated by Johnny Weismuller in the 1930s and 1940s, has been one of Hollywood's most durable archetypes, sturdy and popular even when the films have been cheap and disposable, like last year's Tarzan and the Lost City.