Tom Clancy's Rainbow Six (often shortened to Rainbow Six or R6) is a tactical shooter video game series by Red Storm Entertainment and Ubisoft, marketed under the Tom Clancy's banner of military-themed video games. Based on the novel Rainbow Six by American author Tom Clancy, it revolves around a fictional international counterterrorist organization called "Rainbow". Tom Clancy's Rainbow Six started in 1998 and as of 2024 consists of 13 entries with 6 expansion pack from early installments.

Tom Clancy's Rainbow Six is one of the most popular and most influential tactical shooter series, and early installments in the series helped propel the tactical shooter genre into the mainstream. Since the mid-2010s, a significant esports scene has formed around newer Rainbow Six games.

The original game in the series is Tom Clancy's Rainbow Six (1998).

Tom Clancy's Rainbow Six follows a secret international counterterrorist organization called "Rainbow" (or "Team Rainbow"; capitalization varies between "Rainbow" and "RAINBOW"). The series is set in the canon Tom Clancy's universe, which is mostly shared with Tom Clancy's Splinter Cell and Tom Clancy's Ghost Recon.

Formed in 1999 by the world's military, law enforcement, and intelligence agencies to combat the post-Cold War global rise in terrorism, Rainbow is a rapid reaction force consisting of "operators" from nations and organizations worldwide, ranging from special forces soldiers and police tactical unit members to intelligence officers and field experts, trained and equipped to be the most capable counterterrorist professionals in the world, able to handle any terrorist attack, hostage rescue, or takedown that local authorities cannot conduct in an effective, reliable, or timely manner. Rainbow is headquartered in Hereford, England, but has global jurisdiction and can base themselves at any intelligence agency's headquarters (such as Langley, Virginia) should their continued presence in a region be necessary.

Due to the sensitive nature of their operations, such as being deployed in multinational incidents or against threats possessing weapons of mass destruction, and to simply prevent terrorists from knowing of their existence, Rainbow operates in complete secrecy, with only the most senior government, military, and intelligence officials knowing they even exist. Cover-ups are often conducted after Rainbow's deployments to disguise operators as local police or military units, omit details that could alarm the public, or prevent the reporting of certain deployments.

The leader of Rainbow is designated "Rainbow Six" (or just "Six"), a reference to the American rank code for captain (O-6).^[2] The first Six was former U.S. Navy SEAL and CIA operations officer John Clark, who led the organization from its founding until his retirement.^{[lower-alpha 1]} Since then, numerous individuals have taken the role of Six, the most recent being Harry Pandey.^{[lower-alpha 2]}

Though the Rainbow Six universe is generally grounded in reality and maintains its basic premise, recent installments and plot events partially depart from the series' established setting or Rainbow's traditional policies, with Rainbow hosting a publicly-visible tactical competition,^{[lower-alpha 2]} recruiting non-government or independent operators such as private military company "Nighthaven",^{[lower-alpha 2]} and being deployed to defeat invading extraterrestrials.^{[lower-alpha 3]}

The first game was developed by Red Storm Entertainment, while the novel was being written.^[3] Red Storm was acquired in 2000 by Ubisoft, which has continued to manage the series ever since.^[4]