X1, X-1 or X-one may refer to:

Transportation

Aircraft

* Bell X-1, the first aircraft to exceed the speed of sound in controlled level flight

Automobiles

* BMW X1, a 2009–present German subcompact luxury SUV * Geely Yuanjing X1, a 2017–2021 Chinese mini crossover * Lada X-1, a 1981 Soviet concept MPV * McLaren X-1, a 2012 British one-off sports car based on the 12C * Red Bull X1, the former name of the Red Bull X2010, a fictional car created for the game ''Gran Turismo 5'' * Wrightspeed X1, a 2008 electric sports car prototype based on the Ariel Atom

Bus routes

* List of Metrobus routes (Washington, D.C.), X1 (Metrobus), a bus route in Washington, District of Columbia, United States * X1 (New York City bus), a bus route in New York City, New York, United States * X1 Steel Link, a bus rapid transit service between Sheffield, Rotherham, and Maltby in England, United Kingdom * Excel (bus network), Excel X1, a bus route from Lowestoft to Peterborough in England, United Kingdom * X1 Glasgow–Hamilton, a former bus route in Scotland

Cycles

* Sinclair X-1, an electrically assisted faired recumbent bicycle * Yamaha X-1, a commuter-style motorbike

Rail transport

* SL X1, a former Swedish commuter train built by ASEA * LNER Class X1, a single locomotive rebuilt several times in it’s history

Watercraft

* X1 (dinghy), a fast, light-weight sailing dinghy designed for inland racing * X-1 Submarine, the United States Navy's only midget submarine * HM Submarine X1, a Royal Navy submarine

Technology

* Sharp X1, a Japanese home computer manufactured by the Sharp Corporation * Xbox One, a video game console * a one-lane PCI Express slot * Cray X1, a supercomputer sold since 2003 * Electrologica X1, an early Dutch computer * Sony Ericsson XPERIA X1, a mobile phone * ThinkPad X1 Carbon, a high-end notebook computer released by Lenovo in 2012 * X1 (software company) formerly known as X1 Technologies, Inc. * Tegra X1, a system on a chip released by Nvidia in 2015 * X1, an IPTV-based cable television hardware platform developed by Comcast

Arts, entertainment, and media

* X1 (band), a South Korean boy band formed through ''Produce X 101'' * X1 (rapper) (1979–2007), American rapper * X Minus One, a 1950s American radio show * X-Men (film), ''X-Men'' (film), the first film in the ''X-Men'' franchise * X-One, monthly magazine produced by Imagine Publishing

Other

* ''x''⁻¹, the multiplicative inverse of ''x'' (another way to denote ''1⁄x'', one divided by ''x'') * Cygnus X-1 and Scorpius X-1, two astronomical x-ray sources * M82 X-1, a candidate intermediate-mass black hole detected in January 2006 * United States patent X1, by Samuel Hopkins (inventor) * X1-(letter T) bread bun - feminine (Egyptian t hieroglyph), X1 (Egyptian hieroglyph t), an extremely common alphabetic letter in the Ancient Egyptian alphabet