Khwarazm (/xwəˈræzəm/; Old Persian: Hwârazmiya; Persian: خوارزم, Xwârazm or Xârazm) or Chorasmia (/kəˈræzmiə/) is a large oasis region on the Amu Darya river delta in western Central Asia, bordered on the north by the (former) Aral Sea, on the east by the Kyzylkum Desert, on the south by the Karakum Desert, and on the west by the Ustyurt Plateau. It was the center of the Iranian Khwarezmian civilization until the 9th century, when Turkic tribes moved into and ruled the lands. A series of kingdoms^{[clarification needed]} such as the Afrighid dynasty and the Anushtegin dynasty, whose capitals were (among others) Kath, Gurganj (now Konye-Urgench) and—from the 16th century on—Khiva. Today Khwarazm belongs partly to Uzbekistan and partly to Turkmenistan.

Khwarazm has been known also as Chorasmia, Khaurism, Khwarezm, Khwarezmia, Khwarizm, Khwarazm, Khorezm, Khoresm, Khorasam, Kharazm, Harezm, Horezm, and Chorezm.

In Avestan the name is Xvairizem; in Old Persian 𐎢𐎺𐎠𐎼𐏀𐎷𐎡𐏁 u-v-a-r-z-mi-i-š or 𐎢𐎺𐎠𐎼𐏀𐎷𐎡𐎹 u-v-a-r-z-mi-i-y (/^hUvārazmī-/); in Modern Persian: خوارزم Xārazm; in Arabic: خَـوَارِزْم Khawārizm; in Old Chinese * qʰaljɯʔmriɡ (呼似密); in Modern Chinese Huālázǐmó (花剌子模 / Xiao'erjing: خُوَلاذِمُوْ); in Tajik: Хоразм, Xorazm, خوارَزم; in Kazakh: Хорезм (Xorezm), حورەزم; in Uzbek: Xorazm, Хоразм, خورەزم; in Turkmen: Horezm, Хорезм, خوْرِزم; in Azerbaijani: Xarəzm, Харәзм; in Turkish: Harezm; in Greek language Χορασμία (Chorasmía) and Χορασίμα (Chorasíma) by Herodotus.

The Arab geographer Yaqut al-Hamawi in his Muʿǧam al-Buldan wrote that the name was a Persian compound 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, believed the Persian name to be made up of xor (خور 'the sun') and zam (زم 'earth, land'), designating 'the land from which the sun rises', although a similar etymology is also given for Khurasan. Another view is that the Iranian compound stands for 'lowland' from kh(w)ar 'low' and zam 'land'. Khwarazm 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 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.)^{[citation needed]}

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 Khwarazm to be what ancient Avestic texts refer to as Airyanem Vaejah (Airyanəm Vaēǰah; later Middle Persian Ērān-wēz). These sources claim that Old Urgench, which was the capital of ancient Khwarazm 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 in what is now Afghanistan, the northern areas of which were a part of ancient Khwarazm and Greater Khorasan. Others, however, disagree. University of Hawaii historian Elton L. Daniel believes Khwarazm to be the "most likely locale" corresponding to the original home of the Avestan people, and Dehkhoda calls Khwarazm "the cradle of the Aryan tribe" (مهد قوم آریا).

The Khwarezmian scholar Al-Biruni (973–1048) says that the land belonging to the mythical king Afrasiab was first colonised 980 years before Alexander the Great (thus c. 1292 BC, well before the Seleucid era) when the hero of the Iranian epic Siyavash came to Khwarazm; his son Kay Khusraw came to the throne 92 years later, in 1200 BC.^{[citation needed]} Al-Biruni starts giving names only with the Afrighid line of Khwarazmshahs, having placed the ascension of Afrighids in 616 of the Seleucid era, i.e. in 305 AD.^{[citation needed]}