Khwarezm /kwəˈrɛzəm/ or Chorasmia /kəˈræzmiə/ (Persian:خوارزم) is a large oasis region on the Amu Darya river delta in western Central Asia, which borders to the north the (former) Aral Sea, to the east the Kyzylkum desert, to the south the Karakum desert and to the west the Ustyurt Plateau. It was the center of the (indigenous) Khwarezmian civilization and a series of kingdoms, whose capitals were (among others) Kath, Gurganj (the modern Köneürgenç) and, from the 16th century on, Khiva. Today Khwarezm belongs partly to Uzbekistan, partly to Kazakhstan and partly to Turkmenistan.

Khwarezm has been known also as Chorasmia, Khwarezmia, Khwarizm, Khwarazm, Khorezm, Khoresm, Khorasam, Harezm, Horezm, and Chorezm.
In Avestan the name is Xvairizem, in Old Persian Huwarazmish, in Modern Persian خوارزم (Khwārazm), in Arabic خوارزم Khwārizm, in Old Chinese *qʰaljɯʔmriɡ(呼似密), modern Chinese Huālázǐmó (花剌子模), in Kazakh Хорезм, in Uzbek Xorazm, in Turkmen Horezm, in Turkish Harezm, in Greek Χορασμία and Χορασίμα, by Herodotus.
The Arab geographer Yaqut al-Hamawi in his Muʿǧam al-buldan wrote that the name was a compound (in Persian) of khwar (خوار), and razm (رزم), referring to the abundance of cooked fish as a main diet of the peoples of this area.
C.E. Bosworth however, believes the Persian name to be made up of (خور) meaning “the sun” and (زم) meaning “Earth”, designating “the land from which the sun rises”, although the same etymology is also given for Khurasan. Another view is that the Iranian compound stands for “lowland” from kh(w)ar “low” and zam “earth, land.”. Khwarezm is indeed the lowest region in Central Asia (except for the Caspian Sea to the far west), located on the delta of the Amu Darya on the southern shores of the Aral Sea. Various forms of khwar/khar/khor/hor are commonly used also in the Persian Gulf to stand for tidal flats, marshland, or tidal bays (e.g., Khor Musa, Khor Abdallah, Hor al-Azim, Hor al-Himar, etc.)
The name also appears in Achaemenid inscriptions as Huvarazmish, which is declared to be part of the Persian Empire.
Some of the early scholars believed Khwarezm to be what ancient Avestic texts refer to as Airyanem Vaejah (“Ariyaneh Waeje”; later Middle Persian Iran vij).These sources claim that Old Urgench, which was the capital of ancient Khwarezm for many years, was actually Ourva, the eighth land of Ahura Mazda mentioned in the Pahlavi text of Vendidad. However, Michael Witzel, a researcher in early Indo-European history, believes that Airyanem Vaejah was located in what is now Afghanistan, the northern areas of which were a part of ancient Khwarezm and Greater Khorasan. Others, however, disagree. University of Hawaii historian Elton L. Daniel believes Khwarezm to be the “most likely locale” corresponding to the original home of the Avestan people, and Dehkhoda calls Khwarezm “مهد قوم آریا” (“the cradle of the Aryan tribe”).