The article deals with the question whether an unconditional basic income is part of an ideal liberal-egalitarian welfare regime. Analyzing UBI from an ideal-theoretical perspective requires a comparison of the justice performance of ideal welfare regimes instead of comparing isolated institutional designs. This holistic perspective allows for a more systematic consideration of issues like institutional complementarity. I compare three potential ideal welfare regimes from a liberal-egalitarian perspective of justice: An ideal social democratic regime, a mixed regime containing a moderate UBI (...) and a maximal UBI regime where UBI replaces most of the welfare state. These regimes are evaluated with respect to three aspects of justice performance: the scope and neutrality of opportunities provided, institutional complementarities with a dynamic, globalized economy and the policy feedback effects on the political stability of liberal-egalitarian political coalitions. I conclude that the overall performance of a mixed regime is superior to the other regimes. (shrink)