HH12

HH12, HH-12, HH 12, HH.12, may refer to:


 * Mission of Honor (novel), abbreviated "HH12", 12th main-line novel in the Honor Harrington novel series, part of the Honorverse fictional milieu created by David Weber


 * HH12, one of the Hamburger–Hamilton stages in chick development
 * Gonadotropin-releasing hormone (HH12)