boyars (bōyärz´), upper nobility in Russia from the 10th through the 17th cent. The boyars originally obtained influence and government posts 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 advised the prince. When political power shifted to Moscow in the 14th and 15th cent., the boyars retained their influence. However, as the Moscow grand princes consolidated their power, the influence of the boyars was gradually eroded, particularly under Ivan III and Ivan IV. 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 czar. The political turmoil of the so-called time of troubles further weakened the boyars, and in the 17th cent. the rank and title of boyar was abolished by Peter I.