"Xi'an" is the atonal pinyin romanization of the Mandarin pronunciation of its name 西安, which means "Western Peace" in Chinese. (The apostrophe – known in Chinese as a 隔音符號, géyīn fúhào – should be included to distinguish its pronunciation from the single syllable xian.) The name was adopted in 1369 under the early Ming dynasty. Jesuit missionaries recorded its name as "Si-ngan" or "Si-ngan-fou"^[19] from its status as the seat of a prefecture (府, fǔ). This form still appears in the Latin name of the Catholic diocese of Xi'an, archidioecesis Singanensis. The name was later romanized as "Hsi-an" by Wade & Giles and as "Sianfu"^[20] or "Sian"^[18] by the Qing imperial post office, both of which were common until the general adoption of pinyin.

The area of present-day Xi'an has been the site of several important former Chinese cities. The capital of the Western Zhou were the twin cities of Feng and Hao, known collectively as Fenghao, located on opposite banks of the Feng River at its confluence with the southern bank of the Wei in the western suburbs of present-day Xi'an.^[21] The Qin capital Xianyang was erected north of the Wei during the Warring States period and was succeeded by the Western Han capital of Chang'an (長安), meaning "Perpetual Peace", which was located south of the Wei and covered the central area of present-day Xi'an. During the Eastern Han, Chang'an was also known as Xijing (西京) or the "Western Capital", relative to its position to the main capital at Luoyang. Under the Sui, its name became Daxing (大興, "Greatly Prosperous") in AD 581. Under the Tang, the name reverted to Chang'an in 618.^[18] Under the Mongolian Yuan dynasty (13th & 14th centuries), it held a succession of names: Fengyuan (奉元), Anxi (安西, "Peaceful West") and Jingzhao (京兆). The Ming name "Xi'an" was changed back to Xijing ("Western Capital", as above) between 1930 and 1943.