X4, X-4 or x4 may refer to: * BMW X4, a German crossover automobile * Sehol X4, a Chinese crossover automobile * Honda X4, a Japanese motorcycle * Moto X4, an Android Smartphone * ''Mega Man X4'', a video game * Robby Naish, Naish X4, a kitesurfing kite * The Norteños street gang * Northrop X-4 Bantam, an early jet age research aircraft * A common name for petroleum ether * A four-lane PCI Express slot * Ruhrstahl X-4, a German World War II air-to-air guided missile * Ultimate X4, a comic-book crossover in the Ultimate Marvel Universe * X4 (New York City bus), an express bus route * Stagecoach Gold bus route X4, a bus route in the United Kingdom * X4 virus, a T-cell tropic HIV * ''X-Men Origins: Wolverine'', a 2009 film * ''X-Men: Days of Future Past'', a 2014 film * WordPerfect X4, a version of word processing software * ''X4: Foundations'', a 2018 video game

See also