The Zealots of Piety (Russian: Кружок ревнителей благочестия, romanized: Kružok revnitelej blagočestija) was a circle of ecclesiastical and secular individuals beginning in the late 1630s in Russia at the time of church schism, which gathered around Stefan Vonifatiyev, the confessor of tsar Alexei Mikhailovich.
The members believed the massacres and conflagrations of the time to be the manifestation of a wrathful God, angry with the Russian people's lack of religiosity.
The Zealots of Piety included Fyodor Rtishchev, Archmandrite Nikon (Minin) of the Novospassky Monastery (future Patriarch of Moscow and All Russia), archpriests Ivan Neronov of the Kazan Cathedral, Avvakum Petrov, Loggin, Lazar, and Daniil.
The members of the Zealots of Piety wanted to enhance the authority of the Russian Orthodox Church and increase its influence upon the people.
The Zealots of Piety soon became the actual rulers of the Russian Orthodox Church, thanks to the support from the tsar, who had paid much attention to the advice of his confessor.