The International Criminal Court (ICC) is a court of last resort for the prosecution of serious international crimes, including genocide, war crimes, and crimes against humanity. Its treaty, the Rome Statute, was adopted in July 1998. The court began work in 2003, following ad hoc tribunals set up in the 1990s to deal with atrocity crimes committed in the former Yugoslavia and Rwanda. 20 years after the Rome Statute, the ICC has made significant headway in bringing global attention to accountability. But it has faced setbacks, and as human rights crises marked by international crimes continue to proliferate, its mandate has proven to be both more needed and more daunting than its founders envisioned. To be effective, the court and its member countries will need to rise to the challenge.