Deoksugung (Korean: 덕수궁; Hanja: 德壽宮), also called Deoksu Palace or Deoksugung Palace, is a former royal palace in Seoul, South Korea. It was the first main palace of the 1897–1910 Korean Empire and is now a major tourist attraction. It has a mix of traditional Korean and Western architecture that reflects its history. Inside the palace are the Daehan Empire History Museum and the National Museum of Modern and Contemporary Art, Deoksugung branch.

The palace was first used as a temporary palace by King Seonjo during the 1592–1598 Imjin War, when the other palaces had been destroyed. In 1611, it was made an official palace named Gyeongungung (it was renamed "Deoksugung" in 1907). The palace then went largely unused until the late 19th century.

In 1897, Gojong declared the creation of the Korean Empire and made Gyeongungung the empire's main palace. He attempted to make the palace a symbol of Korea's efforts to modernize. He rapidly expanded it by acquiring land from nearby properties and constructing new buildings in both Korean and Western styles. Under his tenure, the palace's major buildings Junghwajeon and Seokjojeon were constructed. Despite his efforts to keep Korea independent, he was forced to abdicate in 1907 and Korea was colonized by Japan in 1910. He lived in the palace until his death in 1919.

After Gojong's death, the colonial government moved quickly to sell off and dismantle the palace's property. By 1930, 18 of the original buildings were left. In 1933, the palace was made a public park. In 1938, a West Wing was constructed for Seokjojeon, and together the two buildings became the Yi Royal Family Art Museum [ko]. After these efforts to open the palace to the public, just 8 of the original buildings remained.

Even for decades after the 1945 liberation of Korea, the palace continued to function as a public park, with some public works projects further altering or decreasing the size of the palace. One scholar estimated the palace's current size to be 1/3rd of its peak size. Efforts to restore its pre-colonial appearance began in the 1980s. In 2004, a comprehensive plan to restore aspects of the palace was enacted. As part of this plan, a number of buildings and structures have been recreated or moved back to their original pre-colonial spots based on historical research.

The site the palace now occupies once contained the tomb of Queen Sindeok, the second wife of the Joseon founding king Taejo (r. 1392–1398). During the reign of Taejong (r. 1400–1418), the tomb was moved elsewhere. Grand Prince Wolsan, the elder brother of King Seongjong, constructed his residence in the area. In the early stages of the 1592–1598 Imjin War, King Seonjo fled Seoul. In his absence, the palaces in the city were destroyed by fire. Upon his return to Seoul in 1593, he stayed in the area, which was dubbed the Jeongneung-dong Haenggung (정릉동 행궁; 貞陵洞行宮). He would eventually die there.

King Gwanghaegun then ascended the throne at the palace. In 1611, Changdeokgung was adequately repaired, and Gwanghaegun moved over to that palace. He then upgraded Haenggung to a full palace and selected a new name for it: Gyeongungung (경운궁; 慶運宮). He ordered that Gyeongungung's facilities be maintained so that they could be used as a secondary palace. Several months later, he moved back to Gyeongungung. While repairing other palaces, he ordered that several of Gyeongungung's structures be disassembled and their materials used in other palaces. In 1618, Seonjo's former wife Queen Inmok was forcefully confined in the palace. In 1623, King Injo ordered that all buildings except for two in Gyeongungung be returned to their original owners.

For much of the later Joseon period, Gyeongungung was considered to have lesser facilities, and thus went largely unused by the Korean royal family. It was renovated in 1679 and visited four times by King Yeongjo between 1748 and 1775. An article in the Encyclopedia of Korean Culture argues it was otherwise disregarded to the extent of not appearing on a number of late Joseon maps. After 1884 failed Gapsin Coup, various foreign missions were granted permission to be established around Gyeongungung. To its west was the Russian legation [ko] and American legation [ko]. To its north is the Embassy of the United Kingdom. In 1893, the Korean monarch Gojong held a ceremony at Gyeongungung for the 300th anniversary of Seonjo returning to Seoul. Historian An Chang-mo (안창모) argues that the palace held symbolism to Gojong as a place where the monarch stayed during a foreign invasion crisis.