The Year in Review seeks to provide readers with an overview of developments with significant relevance to international humanitarian law (IHL)/the law of armed conflict (LOAC) that took place during 2021. More specifically, the Year in Review assesses: (i) potential situations of armed conflict, including a classification of them as international or non-international armed conflicts, belligerent occupation, or situations not meeting the relevant legal requirements for the application of IHL; (ii) a summary of relevant proceedings and developments relating to the prosecution of serious violations of IHL-war crimes-at international, hybrid, and domestic courts and tribunals; and, (iii) an overview of developments in the IHL-related fields of arms control and disarmament.