In the wake of Russia’s unprovoked invasion of Ukraine, there is broad consensus–atleast in the Global North1–that Russian leaders must be prosecuted for the crime ofaggression. That consensus, however, does not extend tohowRussian aggressionshould be prosecuted. Some commentators argue that the International Criminal Court(ICC) is the most appropriate forum, even if enlivening the Court’s jurisdiction requiresamending the Rome Statute. Others call either for an ad hoc international tribunalsimilar to the ICTY and ICTR or for a hybrid tribunal based in the Ukrainian judicialsystem and supported by the Council of Europe. And still others advocate for nationalprosecutions conducted by Ukraine itself or by third states that have universal jurisdictionover aggression.This article provides a critical assessment of the various options for prosecuting Russianleaders for their role in the invasion of Ukraine. The article is divided into three sections.Section 1 explains why Russia’s invasion of Ukraine violates the prohibition of the use offorce in Art. 2(4) of the UN Charter and amounts to a criminal act of aggression undereither customary international law or the Rome Statute. It also briefly addresseswhether Belarus’s support for Russia’s invasion was itself a criminal act. Section 2, theheart of the article, assesses three potential international options for prosecuting the indi-viduals responsible for Russian aggression, paying particular attention to issues of immu-nity and selectivity. Finally, Section 3 examines proposals for domestic prosecutions inUkraine or elsewhere.