“Illiberalism” has assumed an invigorated if unanticipated significance in the 21st century. Aspects of illiberalism populate not only states long known as indifferent to such principles as personal liberty, human equality and the rule of law but have expanded in “liberal” democracies as their rulers employ purportedly “illiberal” practices more frequently than in the recent past. Indeed, the term “illiberal” seems to have lost its negative aura in the context of state action. We contend that illiberalism represents either an opposition to procedural democratic norms—as disruptive illiberalism—or an ideological struggle—termed ideological illiberalism. We first discuss the term as used in the vast literature on regime types in the debate on authoritarian/democratic hybrid-regimes. We then turn to the key puzzle in what one may call “illiberalism studies”: the rise of illiberal practices and policies in liberal democracies. To inform our analysis empirically, we investigate the ways in which illiberal arguments and institutions (notably camps) were deployed historically and in immigration policy. We conclude with an example of illiberal policy from modern day Hungary.