For many decades, scholars assumed voluntary compliance and citizens’ commitment to a regime’s principles and values to be critical for regime stability. A growing literature argues that indoctrination is essential to achieve this congruence. However, the absence of a clear definition and comprehensive comparative measures of indoctrination have hindered systematic research on such issues. In this paper, we fill this gap by synthesizing literature across disciplines to clarify the concept of indoctrination, focusing particularly on the politicization of education and the media. We then outline how the abstract concept can be operationalized, and introduce and validate an original expert-coded dataset on indoctrination that covers 160 countries from 1945 to the present. The dataset should facilitate a new generation of empirical inquiry on the causes and consequences of indoctrination.