The BBC makes and broadcasts the British version of Dragon's Den.
The programme became part of the BBC’s factual-entertainment output after its British launch in 2005. Its format combines business advice, investment negotiation and reality television, with entrepreneurs presenting their ideas to a panel of potential investors.
This answer refers to the British broadcaster, not to the companies that produce versions of the format overseas. Dragon's Den has international adaptations, including programmes in Canada, Australia, Ireland and other markets, and those versions belong to different broadcasters.
The BBC connection is also why the British series is commonly discussed alongside other BBC factual brands rather than commercial British reality franchises. The broadcaster’s version uses the British spelling “Dragon's Den” and its own rotating panel of investors.