Seongbuk District (Korean: 성북구) is one of the 25 districts of Seoul, South Korea. The district is located in the mid-north part of the city. The current mayor is Lee Seung-ro, who has been mayor since July 2018. Seongbuk District was established under Presidential Decree No. 159 on August 13, 1949 (including some areas of Dongdaemun District and some areas of Sungin-myeon, Goyang-gun), and was promoted to an autonomous district by implementing a Gu-level local government on May 1, 1988.

The name Seongbuk derives from the Korean term meaning "the north of the capital city," which originally referred to the area situated to the north of the city walls of Hanyang, the former name of Seoul. The designation is believed to have originated during the Joseon Dynasty, a period when the region's location relative to the capital's fortifications gave rise to the name. Over time, the geographical reference to the northern part of the capital has endured, and today is used as the official name of Seongbuk District. Although the district's name changed over the years, Seongbuk was officially adopted as the name in 1949.

Archaeological excavations have not uncovered any prehistoric artifacts or relics in Seongbuk District. However, the area features a typical baesanimsu geographical structure, with Bukhansan and Bugaksan mountains to the northwest and streams such as Jeongneungcheon and Seongbukcheon flowing from the valleys of these mountains. Given this natural environment, it is presumed that people may have settled and lived in the region. During the Three Kingdoms period, the Goguryeo, Baekje, and Silla dynasties engaged in continuous territorial conflicts over the Han River basin. It is likely that the Seongbuk District area also experienced shifts in ruling powers during this period. After Silla unified the Korean Peninsula, the region, including present-day Seoul, was incorporated into Hansanju, one of the administrative districts of Silla. During the reign of King Gyeongdeok, Hansanju was renamed Hanju, and the area was designated as Hanyang-gun, placing Seongbuk District under Hanju's jurisdiction. In 1967, in Samyang-dong, an area adjacent to Seongbuk District and now part of Gangbuk District, the Gilt-bronze Standing Avalokitesvara Bodhisattva of Samyang-dong, Seoul (National Treasure No. 127) was discovered. The statue is believed to date back to the early 7th century, and is attributed to Silla.

Following the establishment of Goryeo by Taejo of Goryeo in 918, the area encompassing present-day Seongbuk District was referred to as Yangju until the reign of King Jeongjong (r. 1035–1046). From the reign of King Munjong (r. 1046–1083) until the reign of King Chungnyeol (r. 1275–1308), the region was designated as Namgyeong. After King Chungseon (r. 1308–1313), and throughout the late Goryeo period, it was referred to as Hanyang-bu. A major transportation route connecting the Goryeo capital, Gaegyeong, with Namgyeong (modern-day Seoul) passed through Seongbuk District. The route is believed to have followed the modern-day road connecting Miasageori, Korea University, Sinseol-dong, and Dongdaemun. Several Buddhist relics and temples from the Goryeo period remain along the route, including the Rock-carved Seated Buddha of Botasa Temple, Bomunsa Temple, and Mita Temple. as well as the Gyeongguksa Temple, established in the late Goryeo period, located in Jeongneung-dong.

During the Joseon Dynasty, the Seongbuk District area was part of the Seongjeo Ship-ri, located outside the city walls of Hanseong (modern-day Seoul). In the late Joseon period, the region fell under the jurisdiction of Sungsin-bang and Inchang-bang. The name "Seongbuk" reflects the meaning "the north of the capital city," referring to the area located to the north of the city walls of Hanyang (modern-day Seoul). This name has persisted into modern times. In the 1840 map of Hanyang, Suseon Jeondo, the term "Seongbuk-dong" appears, marking the area. The southern foothills of Bukhansan, which are now part of Seongbuk District, were heavily forested, so much so that wild tigers once roamed the area, prompting the king to lead hunting expeditions to the region. During the Joseon Dynasty, the area now known as Seongbuk was a significant gateway to the northeast of Seoul. The main route connecting Seoul to Gangwon-do and ultimately to Hamgyeong-do passed through the region. This road served as an important trade route, linking merchants and facilitating the exchange of goods, such as daily necessities from Hanyang and various marine products from Hamgyeong-do.

In the late Joseon period, the military unit Eoyeongcheong established a northern garrison (Bukdun) in Seongbuk-dong to protect the city. Soldiers and civilians were tasked with cultivating the land, although the area's poor soil and limited arable land posed challenges. To sustain the population and support the military, the government established systems like the Pobaek and Hunjo industries. These involved the production of unbleached hemp and raw cloth, as well as the preparation of fermented soybeans to supply the royal court.

Seongbuk, which had been located outside the city walls until the Joseon Dynasty, became part of Gyeongseong (now Seoul) in 1936. In the early Japanese colonial era, Seongbuk originally was in Goyang County but later fell under incorporation by Gyeongseong. Between 1914 and 1929, when Seongbuk was not yet part of Gyeongseong, a communal cemetery was established in the area. Due to poor transportation, the inhabitants ended up burying the dead in places relatively close to cities. In addition, traditional funeral practices, like the decoration of the funeral procession and accompanying the corpse to the cemetery, determined where the cemetery was to be located. The Mia-ri communal cemetery, established during this time, was demolished in the mid-1950s, and the area became home to displaced individuals and the poor. The Japanese colonial administration in 1937 began implementing land-redistribution programs in the Donam district, leading to an increase in the district's population. Although the Japanese government finished the reorganization of the land, it was concerned that the suburbs would remain underdeveloped since there was no interest in settlement. To fight this, the government conducted wide-ranging propaganda efforts promoting the idea that living in the suburbs would improve one's living standards, whereas urban life would lead to poverty. This resulted in the construction of what became known as "Joseon-style houses" or urban hanok, which was a blend of traditional Korean architecture and Western-style housing.

As the Donam district expanded into a residential area, the majority of the early residents, who were often poorer families, were relegated to the fringes of the district, namely in the areas around Jeongneung-ri and the Jeongneungcheon stream. Displaced families established temporary settlements referred to as "Tommok-chon" (shantytowns), in which disaster victims built simple houses along riverbanks, embankments, and underneath bridges. With more and more displaced people moving there, the government of Japan formally declared Jeongneung-ri a place for resettling them. It was subsequently leveled in around 1942 when the Japanese army, suffering labor shortages in the middle of World War II, relocated these people to Hokkaido and elsewhere by force. When more people moved to Seongbuk, educational institutions began opening in the area. In the mid-1930s, several schools including Boseong College, which would go on to become Korea University, Gyeongseong Commercial High School, and a few Japanese residents' schools were built. The schools played an important role in the educational history of the district and in establishing the presence of different universities in the area of Seongbuk today. Public transportation such as buses and trams began operating n the district. In 1941, a tram station had been established in Donam-dong near Mia-ri and the city gate to the east.