We empirically test whether ownership concentration contributes to explain the cross-variation in systemic risk contribution for a sample of European banks over the 2004-2016 period and how this effect may vary depending on the largest controlling shareholder category. The results show that higher ownership concentration is associated with greater banks' systemic risk contribution. Deeper analysis indicates that banks' systemic risk contribution is even stronger for banks where institutional investors and states are the largest controlling owners. Overall, our findings contribute to the literature examining the determinants of banks' systemic risk in particular and financial stability as a whole and have several policy implications.