The strigolniki were followers of a Russian religious sect which appeared in the mid-14th century, known as strigolnichestvo. They first appeared in Pskov before spreading to Novgorod and Tver. By the early 15th century, they had disappeared. Along with the Judaizers, they were one of the major sects in medieval Russia.

Proto-Protestantism, also called pre-Protestantism, refers to individuals and movements that propagated various ideas later associated with Protestantism before 1517, which historians usually regard as the starting year for the Reformation era. The relationship between medieval sects and Protestantism is an issue that has been debated by historians.