Daejeon (Korean: 대전; Korean: [tɛdʑʌn] ^ⓘ) is South Korea's fifth-largest metropolis, with a population of nearly 1.5 million. Located in a central lowland valley between the Sobaek Mountains and the Geum River, the city is known both as a technology and research center, and for its close relationship with the natural environment. Daejeon is a major transportation hub, having grown up as a railway town, and is approximately 50 minutes from the capital, Seoul, by KTX or SRT high speed rail.

Daejeon (along with Seoul, Gwacheon and Sejong City) is one of South Korea's administration hubs. The city is home to 23 universities and colleges, including Korea Advanced Institute of Science and Technology (KAIST) and Chungnam National University, as well as government research institutes, and research and development centers for many chaebols such as Samsung, LG, mostly located in the city's Daedeok Yeongu Danji.

From the 1980s, multiple national administrative functions were moved from Seoul to Daejeon, most of which are now located in the Daejeon Government Complex, resulting in another population increase. The city was a sub host for the 1986 Asian Games, hosted the Expo 1993, the International Mathematical Olympiads in 2000 and will be the main host city of the 2027 Summer World University Games. Daejeon and was elevated to the status of Metropolitan City in 1989.

Daejeon is situated in a lowland valley with three major rivers, all of them eventually flowing into the Yellow Sea by way of the Geum river. The city is surrounded by several small mountains, and is located approximately 170 km (106 mi) south of Seoul and 290 km (180 mi) north of Busan, and 70 km (43 mi) east of the Yellow Sea. Daejeon experiences a monsoon-influenced, four-season climate with wet, hot summers and drier, cold winters.

Daejeon is bordered to the east by Boeun County and Okcheon County in North Chungcheong Province, to the west by Gongju and Gyeryong in South Chungcheong Province, to the south by Geumsan County and Nonsan in South Chungcheong Province, and to the north by Sejong Special Self-Governing City and Cheongju in North Chungcheong Province. Its geographical coordinates range from 127°14′ to 127°33′ east longitude and 36°10′ to 36°29′ north latitude. Daejeon covers an area of 539.98 square kilometers and has a population of 1,518,775 as of 2015. Administratively, the city is divided into five districts and 79 administrative neighborhoods (177 legal neighborhoods). The metropolitan city hall is located in Dunsan-dong, Seo District, Daejeon.

The earliest record of the modern name 'Daejeon' is in the 1481 geography book, Tongguk yŏji sŭngnam. 'Daejeon' (대전 大田) is a Hanja translation of the native placeword for the area, 'Hanbat' (한밭), meaning 'Great fields'. 'Hanbat', is a compound word that adds 'Han' (한/often transcribed in Hanja as 韓, as in Korea), that means Great or big, and the word 'Bat' (밭), meaning field, leading to Big/Great Field(s).The 'Han' (한) translated into 'Dae' (大) - both meaning big, and 'Bat' (밭) translated to 'Jeon' (田), both meaning fields.

The name Hanbat is still in use as a road name for Hanbat-daero (한밭대로), or Hanbat road, a road of 12.7 kilometers connecting Daejeon's Yuseong district to Dong-gu.[1]

It is unclear exactly when humans first inhabited the Daejeon area. However, the Paleolithic site of Seokjang-ri in nearby Gongju, Chungcheongnam-do, and the Yongho-dong site in Daedeok District, Daejeon, suggest that people lived here from around that time. From the Bronze Age, artifacts such as bronze items, dwelling sites, and pottery have been excavated, providing concrete evidence of sustained human habitation.