The meaning of khan is: A king; a prince; a chief; a governor; so called among the Turks, and  Persians, and in countries now or formerly governed by them.

The surname Khan originates with the honorific khan, originally used in the Mongol Empire, and later  more widely by Islamic chieftains in South Asia.The British Raj continued the Mughal practice  of awarding titles such as Khan Bahadur for Muslims and Rai Bahadur for Hindus. As a title, khan is now mainly used by the Pashtuns. In the South Asian Subcontinent a Pashtun is  addressed as Khan Sahib routinely whether he has Khan formally as part of his name or not. Moreover,  the term Khawanain is used to refer to the Khans, collectively, as rulers, chiefs etc. of Khanates  in the North West Frontier Province of India, and later Pakistan, particularly in Hangu, Hazara,  Swat, Dir, Mardan and other districts in contemporary Khyber Pakhtunkhwa. In the non-Frontier  regions of the Subcontinent Khanates did not exist at anytime in history.

The communities that use the surname Khan include the Afghans/Pashtuns, Bengalis, Punjabis, Mughals,  Muslim Rajputs,Arains and Turkic people in Central Asia and Northern Pakistan; tribes in Pakistan  and their descendents in India, Baloch tribes in Balochistan and in Sindh and various Mongol, Turks,  and Tatar tribes in central and northern Asia.
 Kahn is also traditionally a Jewish name derived from the Hebrew name Cohen or Kohen or Cohn,  denoting priestly/noble lineage.

Khan is also a last name found in Tatars, a Muslim Turkic speaking group, mostly in Russia. Also  been known to be part with Genghis Khan's army. The name Khan has also been used by the Peoples of  the Caucasus since the region has a history of Turkic and Mongolic (Mughal) rulers. It is now a widespread Islamic surname in most countries of Central and South Asia. Khan is the  surname of over 80,000 Islamic Britons, mostly British Asian, making it the 80th most common surname  in the United Kingdom,

Meaning & Origin:

The ancient surname Khan is a contracted form of Khagan, from the Turkish khan meaning "chief or  ruler." It was originally a hereditary title born by early Mongol leaders, such as the legendary  Genghis Khan, but is now widely used as a surname throughout the Muslim world. Khan is an especially  common surname in South Asian Muslim families, and is also one of the most common surnames in  Pakistan, United kingdom and worldwide.