The Evolution Championship Series, commonly known as Evo, is an American annual esports event that focuses exclusively on fighting games. The tournaments are completely open and use the double elimination format. As with Super Battle Opera, contestants travel from all over the world to participate, including gaming hubs such as Japan, South Korea and Pakistan. The first Evolution was originally held as a Super Street Fighter II Turbo and Street Fighter Alpha 2 tournament called the Battle by the Bay. It changed its name to Evo in 2002. Every successive tournament has seen an increase of attendees. It has been held at various venues across the Las Vegas Valley since 2005. From 2021 to 2025, the event was jointly owned by Sony Interactive Entertainment and the Endeavor esports venture RTS. As of 2025, Indian esports tournament operator NODWIN Gaming, as well as RTS (now owned by the Saudi megaproject Qiddiya), jointly own Evo.

Evo was founded by Tom Cannon, also known for his work on Shoryuken.com, a fighting game website. The tournament started as "Battle by the Bay", a 40-man Super Street Fighter II Turbo and Street Fighter Alpha 2 tournament in 1996 in Sunnyvale, California. The event eventually moved to its recurring venue in the Las Vegas Valley, Nevada. The event changed its name to Evolution Championship Series, or EVO for short, in 2002. Over time, the tournament grew, recording over one thousand participants in 2009.

Originally the tournament used arcade cabinets, but in 2004 the decision was made to move all games over to their console versions, to a large amount of controversy. During the transition to games on the seventh generation consoles, most games were played on a PlayStation 3, though Evo 2014 ran most games on the Xbox 360. Aside from the official tournaments, there is also a "BYOC" ("bring your own console") area in which many different games are played and side tournaments are held.

B3: Battle by the Bay was organized by Tom "inkblot" Cannon, Tony "Ponder" Cannon, Joey "MrWizard" Cuellar, and Seth "S-Kill" Killian, and held in the Golfland arcade hall in Sunnyvale, California. The tournament had 40 contenders mostly from the United States, though B3 also featured players from Canada and Kuwait. B3 featured a Super Street Fighter II Turbo and Street Fighter Alpha 2 tournament.

The B4 Street Fighter Championships were held on July 15–16, 2000, in Folsom, California. B4 introduced several new Capcom fighting games to the roster: Street Fighter Alpha 3, Street Fighter III: 3rd Strike, and Marvel vs. Capcom 2: New Age of Heroes. The newly released Marvel vs. Capcom 2 was the first non-Street Fighter game to be included, and a precedent for the tournament to branch out to other games. The Capcom Versus series has since had a large presence in the Battle of the Bay and Evolution Championship Series events.

Held in August 2001 in Folsom, California, the B5 Championships was attended by a much larger international crowd, particularly from Japan. Capcom vs. SNK: Millennium Fight 2000 made its introduction in the tournament roster at B5, and Marvel vs. Capcom 2 was again a headliner of the event, being described by TechTV as "the hottest arcade fighting game of the season."

In 2002, the event became formally known as its current name, "Evo". Evo 2002 took place on August 9, 2002, at the University of California, Los Angeles.

Evo 2004 took place at California State Polytechnic University, Pomona in Southern California from July 29 to August 1. The tournament amassed approximately 700 competitors from over 30 countries to compete in over nine different games. The games featured included Super Street Fighter II Turbo, Street Fighter III: 3rd Strike, Marvel vs. Capcom 2, Capcom vs. SNK 2, Virtua Fighter 4: Evolution, Guilty Gear XX, Soulcalibur II, Tekken 4, and Tekken Tag Tournament.