Military service often requires engaging in activities, witnessing acts, or immediate decision‐making that may violate the moral codes and personal values to which most individuals ascribe. If unacknowledged, these factors can lead to injuries that can affect the physical, psychological, social, and spiritual health of military men and women. The term moral injury has been assigned to these soul‐ceasing experiences. Although researchers have attempted to define moral injury and what leads to such experiences, inconsistencies across definitions exist. In addition, nearly all existing definitions have lacked empirical support. The purpose of the present systematic review was to explore how moral injury has been defined in research with military populations, using Cooper's approach to research synthesis as well as PRISMA guidelines. An in‐depth review of 124 articles yielded 12 key definitions of moral injury across the literature. Two of these 12 definitions were grounded in empirical evidence, suggesting that much more research is needed to strengthen the face validity and reliability of the construct. Quality rankings were developed to categorize each of the included articles. The findings punctuate the need for empirical evidence to further explore moral injury, particularly among samples inclusive of service members and the biopsychosocial–spiritual experiences associated with such injuries.

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