Research on truth commissions, and transitional justice more generally, has been hampered by the lack of detailed, comparable, cross-national data. These limitations are especially acute as we seek to investigate variations across transitional justice measures and the impact of those measures. We propose to complete an in-progress data set entitled the Global Truth Commission Index. This data set codes details of forty-six truth commissions around the world on three hundred in-depth variables including the design phase, operational phase, and final report. Once complete, this will be the most in-depth, detailed data set of truth commissions in existence. This data set will be able to support fine-grained cross-national research projects that will shed light on the design and implementation of truth commissions and, subsequently, on the impact of those truth commissions on a variety of other significant variables affecting post-conflict societies. I am especially interested in the impact of truth commissions on democratization, human rights accountability, rule of law developments, public security, and social inclusion cross-nationally. Other scholars across disciplines will find it valuable for understanding regional disparities, economic development, and memory politics, among others. Furthermore, this data set will ultimately be made public so that it can inform the design and operation of future truth commissions. This work in 2021-22 to complete this data set lays the groundwork for numerous future projects, including articles on the impact of truth commissions on political inclusion of women and minority groups and the relationship between truth commissions and justice system reforms.