Despite recent advances in gender equality in political representation and the availability of resources, this article shows that there is a persistent gender gap in declared political interest over the life cycle. Using evidence from the British Household Panel Survey (BHPS), we track the gender gap through the life span of citizens. At age 15, there is already a substantial gender gap of 20 percentage points in the probability of respondents reporting being politically interested, pointing to gendered socialization processes as the key explanation for such differences. In the following 10 years, as people develop into adults and unravel their political orientations, the extent of the gender gap continues to grow by about 10 additional percentage points. Following these formative years, attitudes crystallize and so does the gender gap, remaining at the same size (around 30 percentage points of difference between women and men) over the life course. These findings suggest that the development of gender roles during early childhood is a crucial phase in the source of the gender gap, deserving further attention from scholars.