A member of the highest non-princely class of medieval Russian society. In the 10th to 12th centuries the boyars formed the senior levels of the princes’ retinues. They received large grants of land and exercised considerable independent power during the period of decentralization after the 13th-century Mongol conquest. However, as the grand princes of Muscovy consolidated their own power, they managed to curb boyar independence.

From the 15th to the 17th centuries Muscovite boyars formed a closed aristocratic class drawn from about 200 families. They retained a stake in princely affairs through their membership of the boyar duma or council. Ivan IV (the Terrible) (ruled 1547–84) reduced their power significantly by relying on favourites and locally elected officials. Their social and political importance continued to decline throughout the 17th century and Peter I eventually abolished the rank and title.