The Collaborative International Dictionary of English v.0.48:

Dramatist \Dram"a*tist\, n. [Cf. F. dramatiste.]
   The author of a dramatic composition; a writer of plays.
   [1913 Webster]

WordNet (r) 3.0 (2006):

dramatist
    n 1: someone who writes plays [syn: dramatist, playwright]

The Devil's Dictionary (1881-1906):

DRAMATIST, n.  One who adapts plays from the French.