A boyar (also spelt bojar; Romanian: boier) was a member of the highest rank of the feudal Ruthenian (Russian) and Romanian aristocracy, second only to the ruling princes, from the 10th through the 17th century.
Boyars in Ruthenia
In the Russian language, the singular is boyarin (боярин), the plural is boyare. Boyars wielded considerable power through their military support of the Kievan princes. Their power and prestige, however, soon came to depend almost completely on landownership.
The boyars occupied the highest state offices and through a council (Duma) advised the prince. They received extensive grants of land and, as members of the Boyars' Duma, were the major legislators of medieval Ruthenia.
When political power shifted to Moscow in the 14th and 15th centuries, the boyars retained their influence. However, as the Grand Dukes of Muscovy consolidated their power, the influence of the boyars was gradually eroded, particularly under Ivan III and Ivan IV.
Tsar Ivan IV "Ivan the Terrible" severely restricted their powers during the 16th century. Their ancient right to leave the service of one prince for another was curtailed, as was their right to hold land without giving obligatory service to the tsar.
The Boyar Duma was finally abolished by Tsar Peter the Great in 1711 in his extensive reforms of government and administration.