principicide

noun2

1. •
   (rare) The killing of a prince.

   • The Roumanians hold the world record for principicide, or the assassination of princes, with Serbia—whose record in this regard is not to be despised, either—a bad second. — 1919
2. •
   (rare) One who kills a prince.

   • The law has been vindicated, and the outraged feelings of the people of these colonies have been avenged by the execution this morning of the wretched man—the would-be principicide [Henry O’Farrell]. — 1868