18D/Perrine–Mrkos is a periodic comet in the Solar System, originally discovered by the American-Argentine astronomer Charles Dillon Perrine (Lick Observatory, California, USA) on December 9, 1896.
A. Henríquez Santana na Kanarskih otokih, malo pozneje je še Ramón Naves iz Barcelone opazil, da je komet povečal magnitudo na 7,3 .