An uyezd (Russian: , ujézd, IPA: [?'jest]) was an administrative subdivision of the Grand Duchy of Moscow, the Russian Empire, and the early Russian SFSR, which was in use from the 13th century. For most of Russian history, uyezds were a secondary-level of administrative division. By sense, but not by etymology, uyezd approximately corresponds to the English term county.
Originally describing groups of several volosts, they formed around the most important cities. Uyezds were ruled by the appointees (namestniks) of a knyaz and, starting from the 17th century, by voyevodas.
In 1708, an administrative reform was carried out by Peter the Great, dividing Russia into governorates. The subdivision into uyezds was abolished at that time but was reinstated in 1727, as a result of Catherine I's administrative reform.
By the Soviet administrative reform of 1923-1929, most of the uyezds were transformed into raions (districts). In Ukraine, uyezds were reformed into forty okrugs which between 1925 and 1930 were the primary-level of administrative division.