Security companies of the United Kingdom

G4S is a British multinational private security company headquartered in London, England, and a subsidiary of Allied Universal. The company was set up in July 2004 when London-based Securicor amalgamated with Danish firm Group 4 Falck (itself the result of a merger between Group 4 and the former security division of Falck a few years prior).

is a Japanese security company headquartered in Tokyo, Japan. It has operations in Japan, United Kingdom, Australia, New Zealand, South Korea, Taiwan, China, Thailand, Vietnam, Malaysia, Singapore, Indonesia, and Myanmar.

Securicor plc was one of the United Kingdom's largest security businesses. It was once a constituent of the FTSE 100 Index but merged with Group 4 Falck in 2004.

British private military company