We advance the understanding of the philosophy and psychology of curiosity by operationalizing and constructing an empirical measure of Nietzsche’s conception of inquisitive curiosity, expressed by the German term Wissbegier, (“thirst for knowledge” or “need/impetus to know”) and Neugier (“curiosity” or “inquisitiveness”). First, we show that existing empirical measures of curiosity do not tap the construct of inquisitive curiosity, though they may tap related constructs such as idle curiosity and phenomenological curiosity. Next, we map the concept of inquisitive curiosity and (...) connect it to related concepts, such as open-mindedness and intellectual humility. The bulk of the paper reports four studies: an Anglophone exploratory factor analysis, an Anglophone confirmatory factor analysis, an informant study, and a Germanophone exploratory and confirmatory factor analysis. (shrink)