The X-Men are a fictional team of superheroes appearing in American comic books published by Marvel Comics. Created by writer Stan Lee and artist/co-writer Jack Kirby, the characters first appeared in The X-Men #1 (September 1963). They are among the most recognizable and successful intellectual properties of Marvel Comics, appearing in numerous books, television shows, films, and video games. The X-Men are Mutants, a subspecies of humans who are born with superhuman abilities activated by the "X Gene". The X-Men fight for peace and equality between normal humans and mutants in a world where antimutant bigotry is fierce and widespread. They are led by Charles Xavier, also known as Professor X, a powerful mutant telepath who can control and read minds. Their archenemy is Magneto, a powerful mutant with the ability to generate and control magnetic fields. Both have opposing views and philosophies regarding the relationship between mutants and humans. While the former works towards peace and understanding between mutants and humans, the latter views humans as a threat and believes in taking an aggressive approach against them, though he has found himself working alongside the X-Men from time to time. Professor X is the founder of Xavier's School for Gifted Youngsters at a location commonly called the X-Mansion, which recruits mutants from around the world. Located in Salem Center in Westchester County, New York, the X-Mansion is the home and training site of the X-Men. The founding five members of the X-Men who appear in The X-Men #1 (September 1963) are Angel (Archangel), Beast, Cyclops, Iceman, and Marvel Girl (Jean Grey); Professor X and Magneto also made their first appearances in The X-Men #1. Since then, dozens of mutants from various countries and diverse backgrounds have held membership as X-Men.

The X-wing starfighter is a fictional starfighter from the original and sequel Star Wars trilogies and the Star Wars expanded universe. They are depicted as the primary space superiority interceptor and dogfighter of the Rebel Alliance, the New Republic and the Resistance. The craft has been merchandised as a variety of toys, models licensed for use in games, novels and comics.

Xbox One is a line of eighth generation home video game consoles developed by Microsoft. Announced in May 2013, it is the successor to Xbox 360 and the third console in the Xbox family. It was first released in North America, parts of Europe, Australia, and Brazil in November 2013, and in Japan, China, and other European countries in September 2014. It is the first Xbox game console to be released in China, specifically in the Shanghai Free-Trade Zone. Microsoft marketed the device as an "all-in-one entertainment system". The Xbox One line mainly competes against consoles such as Sony's PlayStation 4, Nintendo's Wii U and Switch, and Apple's 4th generation TV. Moving away from its predecessor's PowerPC-based architecture, Xbox One marks a shift back to the x86 architecture used in the original Xbox; it features an AMD Accelerated Processing Unit (APU) built around the x86-64 instruction set. Xbox One's controller was redesigned over the Xbox 360's, with a redesigned body, D-pad and triggers capable of delivering directional haptic feedback. The console places an increased emphasis on cloud computing, as well as social networking features, and the ability to record and share video clips or screenshots from gameplay, or live-stream directly to streaming services such as Mixer and Twitch. Games can also be played off-console via a local area network on supported Windows 10 devices. The console can play Blu-ray Disc, and overlay live television programming from an existing set-top box or a digital tuner for digital terrestrial television with an enhanced program guide. The console optionally included a redesigned Kinect sensor, marketed as the "Kinect 2.0", providing improved motion tracking and voice recognition for use in its graphical user interface (GUI) and games. Xbox One received mostly positive reviews for its refined controller design, multimedia features, and voice navigation. Its quieter and cooler design was praised for making the console more reliable than its predecessor on-launch, but the console was generally criticized for running games at a technically lower graphical level than the PlayStation 4. Its original user interface was panned for being nonintuitive, although changes made to it and other aspects of the console's software post-launch received positive reception. Its Kinect received praise for its improved motion-tracking accuracy, its face recognition logins, and its voice commands. In August 2016, Microsoft released a refreshed Xbox One model, Xbox One S, which has a streamlined design, support for 4K video playback (including Ultra HD Blu-ray), upscaling of games from 1080p to 4K resolution, as well as HDR10 high-dynamic-range color. It was praised for its smaller size, its on-screen visual improvements, and its lack of an external power supply, but its regressions such as the lack of a native Kinect port were noted. A high-end model, Xbox One X, was unveiled in June 2017 and released in November; it features upgraded hardware specifications, and support for rendering games at 4K resolution.

XCircuit is a Unix/X11 and Windows program for drawing publication-quality electrical circuit schematic diagrams and related figures and the production of circuit netlists through schematic capture. XCircuit regards circuits as inherently hierarchical and writes both PostScript output and hierarchical SPICE netlists. Circuit components are saved in and retrieved from libraries which are fully editable. XCircuit does not separate artistic expression from circuit drawing; it maintains flexibility in style without compromising the power of schematic capture.

The Xella Group with headquarters in Duisburg, Germany, develops, manufactures and markets building and insulation materials. With its Ytong, Silka and Hebel brands, Xella is one of the world's largest manufacturers of autoclaved aerated concrete and calcium silicate units. The Multipor brand stands for non-flammable mineral insulation boards and with Ursa we are one of Europe's leading manufacturers of insulation materials. The Xella group bundles the expertise and know-how of Ytong, Silka, Multipor, Hebel and Ursa and is continuously developing these brands. Xella is one of just a few European building materials companies to operate its own Research and Development Center which focuses its work on three main areas: Product and process research, applied research and construction physics. Xella products are sustainable both in manufacture and use. They also undergo a process of continuous development. The products therefore make an important contribution to the construction of energy-efficient, high-quality buildings and consequently also to environmental protection and the conservation of resources. The products have received numerous awards and certificates for their environmentally friendly characteristics.

Xenix is a discontinued version of the Unix operating system for various microcomputer platforms, licensed by Microsoft from AT&T Corporation in the late 1970s. The Santa Cruz Operation (SCO) later acquired exclusive rights to the software, and eventually replaced it with SCO UNIX (now known as SCO OpenServer). In the mid-to-late 1980s, Xenix was the most common Unix variant, measured according to the number of machines on which it was installed. Microsoft chairman Bill Gates said in 1996 that for a long time that company had the highest-volume AT&T Unix license.

Xenon is a chemical element with symbol Xe and atomic number 54. It is a colorless, dense, odorless noble gas found in the Earth's atmosphere in trace amounts. Although generally unreactive, xenon can undergo a few chemical reactions such as the formation of xenon hexafluoroplatinate, the first noble gas compound to be synthesized. Xenon is used in flash lamps and arc lamps, and as a general anesthetic. The first excimer laser design used a xenon dimer molecule (Xe2) as the lasing medium, and the earliest laser designs used xenon flash lamps as pumps. Xenon is used to search for hypothetical weakly interacting massive particles and as the propellant for ion thrusters in spacecraft. Naturally occurring xenon consists of eight stable isotopes. More than 40 unstable xenon isotopes undergo radioactive decay, and the isotope ratios of xenon are an important tool for studying the early history of the Solar System. Radioactive xenon-135 is produced by beta decay from iodine-135 (a product of nuclear fission), and is the most significant (and unwanted) neutron absorber in nuclear reactors.

XP Power is a manufacturer and supplier of critical power control systems. It is listed on the London Stock Exchange and is a constituent of the FTSE 250 Index.

Xsens Technologies B.V. (or Xsens) is a supplier of 3D motion capture products based upon miniature MEMS inertial sensor technology. The company has created intellectual property in the field of multi-sensor data fusion algorithms, combining inertial sensors with aiding technologies such as GPS, Motion capture and biomechanical modeling. Xsens is part of Mcube the provider of the world’s smallest and lowest power MEMS motion sensors, key enablers for the Internet of Moving Things. Xsens has offices in Enschede (headquarter), the Netherlands, Los Angeles, California, Shanghai and Hong Kong.

Xtralis, now part of Honeywell, was a privately held firm. It manufactures smoke detection, gas detection and video surveillance security products for the early detection, visual verification, and prevention of fire and intrusion threats.