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 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 4X (disambiguation)