The term for a government ruled by a single person with absolute power is an autocracy. In an autocratic system, the leader exercises significant control over all aspects of governance, often with little to no checks on their authority. This concentration of power can lead to abuses of rights, lack of political pluralism, and minimal public participation in decision-making processes. Autocracies may take various forms, including dictatorships or monarchies, but they all center around centralized authority.