Think tanks, or organizations producing and disseminating policy knowledge to influence policymakers, are a given element of political systems around the globe. Depending on the national opportunity structure, think tanks take different forms. Individual think tanks usually represent a given ideological orientation or set of values. This chapter studies think tanks that align with the illiberal political agenda in Poland. These organizations, most of which self-identify as conservative, have played a significant role in the electoral success of Law and Justice, and after the party gained power, they have helped sustain the illiberal political orientation by providing the government with policy ideas and communicating policy decisions to the broader public domestically and abroad. Conservative think tanks form the intellectual infrastructure for the illiberal government, both proactively inspiring the illiberal agenda and reactively legitimizing it to external audiences. Benefiting from illiberal policymaking, they form the illiberal knowledge regime.