The 18th century saw the rise of Enlightened absolutism. Enlightened absolutists were rulers who ruled in an absolute manner and embraced certain Enlightenment principles. Some of them even corresponded with Enlightenment thinkers.
One example of an enlightened absolutist ruler was Frederick the Great of Prussia. Frederick was friends with Voltaire, one of the most prominent enlightenment thinkers. He favored religious toleration and worked for judicial reform in his territories; both standard enlightenment views.
In Russia, enlightened absolutism had another representative in the person of Catherine the Great. Catherine also corresponded with Voltaire, and was friends with Diderot, another Enlightenment thinker. Catherine tried to promote education in Russia, but failed due to low funds and the reluctance of Russian parents to send their children to the schools. She also agreed with religious toleration, to some extent.
Other rulers in this category were Joseph II of Austria and Charles III of Spain. Joseph lifted restrictions on Jews and had a greater degree of religious toleration in his lands than any Catholic country at the time. He also shut down a third of the monasteries in his lands because he thought that they were not being productive to society, another common view of enlightenment thinkers. There were also reforms in the legal system and in the condition of the serfs. He also instituted compulsory education. Charles III tried to lighten the power and scope of the inquisition and bring the church under the authority of the state.