The Czech Republic's official long and short names at the United Nations are Česká republika and Česko in Czech, and the Czech Republic and Czechia in English. All these names derive from the name of the Czechs, the West Slavic ethnolinguistic group native to the Czech Republic. Czechia (//), the official English short name specified by the Czech government, is used by many international organisations.
Attested as early as 1841, then, for example in 1856 or 1866, the word Czechia and the forms derived from it are always used by the authors synonymously with the territory of Bohemia (Kingdom of Bohemia at that time).
The English long form "Czech Republic" is searched online in over 80 % cases but the use of the short form "Czechia" is increasing in time from less than 1 % in 2015 to more than 16 % in 2023. Other languages generally have greater official use of a short form analogous to Česko or Czechia (such as French [la] Tchéquie, or Russian Чехия/Čehija, or Korean 체스꼬/Chesŭkko or 체코/Chekho).
The Czech name Čechy is from the same root but means Bohemia, the westernmost and largest historical region of modern Czechia. The name Bohemia is an exonym derived from the Boii, a Celtic tribe inhabiting the area before the early Slavs arrived. The Lands of the Bohemian Crown (1348–1918) were part of the Holy Roman Empire; often called "the Czech lands", they sometimes extended further, to all of Silesia, Lusatia, and various smaller territories. The Czech adjective český means both "Czech" and "Bohemian".
The Czech Republic's official formal and short names in Czech were decided at its creation after the dissolution of Czechoslovakia in 1992.