Scholars have long noted that couples are more likely to vote compared to individuals who live alone, and that partners' turnout behavior is strongly correlated. This study examines a large administrative dataset containing detailed information about validated turnout and the timing of individuals moving in together, and finds evidence of a substantial and robust increase in turnout after cohabitation. The study exploits the fact that two-voter households moving in together right before an election are comparable to those moving in together right after the election. Depending on the model specification, turnout increases by 3.5 to 10.6 percentage points in the months after taking up cohabitation. Voters are mobilized regardless of their own and their cohabitant's turnout behavior in a previous election. The results are robust to several robustness checks, including benchmarking with singles who move to mitigate the cost of moving in the analysis. The results highlight the importance of social norms and the household's essential role as a proximate social network that increases turnout.