Social scientists increasingly combine multiple datasets to study ethnicity in Africa. We facilitate these efforts by systematically linking over 8’100 ethnic categories from eleven databases including surveys, geographic data, and expert-coded lists. Exploiting the linguistic tree from the Ethnologue database, we propose a systematic solution to the grouping problem of ethnicity. Novel empirical results on trust in African heads of states highlight the importance of explicitly considering sample inclusion criteria and different ways of linking ethnic categories from multiple datasets. An R-package allows researchers to link ethnic groups from any database with explicit rules and to easily add their own data on ethnic groups.