The Collaborative International Dictionary of English v.0.48:

Monarchist \Mon"arch*ist\, n. [Cf. F. monarchiste.]
   An advocate of, or believer in, monarchy.
   [1913 Webster]

WordNet (r) 3.0 (2006):

monarchist
    n 1: an advocate of the principles of monarchy [syn:
         monarchist, royalist]

Moby Thesaurus II by Grady Ward, 1.0:

22 Moby Thesaurus words for "monarchist":
   Bircher, Bourbon, Tory, conservatist, conservative, diehard,
   extreme right-winger, hard hat, imperialist, radical right,
   reactionarist, reactionary, reactionist, right, right wing,
   right-winger, rightist, royalist, social Darwinist, standpat,
   standpatter, ultraconservative