A royalist supports a particular monarch as head of state for a particular kingdom, or of a particular dynastic claim. In the abstract, this position is royalism. It is distinct from monarchism, which advocates a monarchical system of government, but not necessarily a particular monarch. Most often, the term royalist is applied to a supporter of a current regime or one that has been recently overthrown to form a republic.
In the United Kingdom today, the term is almost indistinguishable from "monarchist," because there are no significant rival claimants to the throne. Conversely, in 19th-century France, a royalist might be either a Legitimist, Bonapartist, or an Orléanist, all being monarchists.