A frogman is someone who is trained in scuba diving or swimming underwater in a tactical capacity that includes military, and in some European countries, police work. Such personnel are also known by the more formal names of combat diver, combatant diver, or combat swimmer. The word frogman first arose in the stage name The Fearless Frogman of Paul Boyton in the 1870s and later was claimed by John Spence, an enlisted member of the U.S. Navy and member of the OSS Maritime Unit, to have been applied to him while he was training in a green waterproof suit.

The term frogman is occasionally used to refer to a civilian scuba diver. Some sport diving clubs include the word Frogmen in their names. The preferred term by scuba users is diver, but the frogman epithet persists in informal usage by non-divers, especially in the media and often referring to professional scuba divers, such as in a police diving role.

In the U.S. military and intelligence community, divers trained in scuba or CCUBA who deploy for tactical assault missions are called "combat divers". This term is used to commonly refer to Navy UDTs, Navy SEALs, Navy SARC, and the Navy Explosive Ordnance Disposal (EOD) units. Navy SWCC have frogmen heritage of combat swimming rather than diving, one of the few and most elite units trained in this element. Other Frogmen units include Marine Raiders Marine Recon, elements of US Army Special Forces (aka Green Berets) Combat Divers, Army Ranger Regimental Reconnaissance Company, Air Force Pararescue, Air Force Combat Controllers, and Air Force Special Reconnaissance, as well as operatives of the CIA's Special Activities Center.

In Britain, police divers have often been called "police frogmen".

Some countries' tactical diver organizations include a translation of the word frogman in their official names, e.g., Denmark's Frømandskorpset; others call themselves "combat divers" or similar. Others call themselves by indefinite names such as "special group 13" and "special operations unit".

Many nations and some irregular armed groups deploy or have deployed combat swimmers or divers.