BBC Two originally aired the British television series Dragons' Den.
The programme premiered on BBC Two in January 2005, introducing British viewers to entrepreneurs seeking investment from a panel of businesspeople. Its BBC Two home helped establish the show as a factual-entertainment programme combining negotiation, personal finance and business storytelling.
Dragons' Den later became associated with the wider BBC television network, and its long run has included changes in presenters, investors and scheduling. Those later developments can make the original channel easy to misremember, particularly because BBC One has also broadcast major entertainment and factual programmes connected with the BBC brand.
The question concerns the programme's original broadcaster, not every channel or service that later carried episodes, repeats or related material. BBC Two is therefore the precise answer for the show's launch-era television home.