In Dragon's Den, an investor who offers money for part of a business is called a Dragon.
The word “Dragon” is the programme's distinctive name for a member of its investor panel. Entrepreneurs enter the den to present their companies and may ask one or more Dragons for a specific amount of money in return for an agreed percentage of equity. A Dragon can accept, reject or negotiate the proposal.
The term is part of the British show's identity and comes from the programme's title. It is not a general legal name for an investor. Outside the show, investors are usually described as angel investors, venture capitalists or private investors, depending on how they provide finance.
Another common confusion concerns the entrepreneur. The entrepreneur owns or represents the business being pitched, while the Dragon is the potential backer. The presenter introduces the programme, but does not normally make the investment decisions. These separate roles are central to understanding the format.