X-Men vs. Street Fighter (Japanese: エックスメン VS. ストリートファイター Hepburn: Ekkusu Men bāsasu Sutorīto Faitā) is a crossover fighting video game developed and published by Capcom. It is Capcom's third fighting game to feature Marvel Comics characters, following X-Men: Children of the Atom and Marvel Super Heroes, and the first installment in the Marvel vs. Capcom series. As the title suggests, the game includes characters from Marvel's X-Men franchise and the cast from Capcom's Street Fighter series. Originally released as a coin-operated arcade game in 1996, it was eventually ported to the Sega Saturn in 1997 and the PlayStation in 1998.X-Men vs. Street Fighter features gameplay similar to Street Fighter, but incorporates dual-character selection and tag team-based combat. Each player selects two characters to compete in a one-on-one battle, attempting to defeat the opposing team. The players are given the ability to switch between their characters at any point during the match. The game also incorporates numerous elements from X-Men: Children of the Atom and Marvel Super Heroes.The game was released to generally positive reviews, with critics praising its gameplay and sprite animation quality. While the Sega Saturn port received praise for maintaining the experience of the original arcade version, the PlayStation port was met with mixed to negative critical reception for removing several features, such as tag team battles. The changes were done in response to the technical limitations of the PlayStation. A sequel to the game, Marvel Super Heroes vs. Street Fighter, was released in 1997.

X-Men: Children of the Atom (Japanese: エックス・メン チルドレン オブ ジ アトム Hepburn: Ekkusu Men Chirudoren obu ji Atomu) is an arcade game that was produced by Capcom and released on the CP System IIarcade hardware in 1994.Based on the X-Men comic book, it is the first fighting game produced by Capcom using characters under license from Marvel Comics. Released around the time of the mid-1990s X-Men animated series, the game features voice actors from the series reprising their roles. The game's plot is based on the "Fatal Attractions" story from the comics - players control one of the X-Men or their enemies in their fight against the villain Magneto. They face each of the other characters in the game in best of three one-on-one fighting matches, before battling Juggernaut and then Magneto himself.The gameplay has much in common with Capcom's previous fighting games, Super Street Fighter II Turbo and Darkstalkers. Children of the Atom adds a combo system that features long combos that can even be performed in mid-air. Also featured in the game are various tactical maneuvers, including the ability for characters to roll. Children of the Atom also introduced multi-tiered fighting environments in which the ground would crumble and characters would fall into lower parts of the level. These concepts and the fast pace of the game would provide the basis for Capcom's Marvel vs. Capcom series, which started with the game's successor X-Men vs. Street Fighter.Ports of the game were released for the Sega Saturn, PlayStation and personal computers. Of these, the PlayStation version was not as well received as the other versions, suffering from slowdown and missing frames of animation.