Keijō (Japanese: 京城), or Gyeongseong (Korean: 경성), was an administrative district of Korea under Japanese rule that corresponds to the present Seoul, the capital of South Korea.

While under colonial rule (1910–1945), the city was called Keijō (京城; 경성; Gyeongseong; Kyŏngsŏng, literally meaning "capital city" in Hanja.).

Gyeongseong was part of Gyeonggi Province, instead of being an independent city or prefecture as in Joseon and present days.

In 1936, Gyeongseong expanded itself as it annexed Yeongdeungpo from Siehung County (Now Siehung City) and recombined some parts of former Gyeongseong districts (Sungin, Yeonghee, etc.)

The central district of Gyeongseong was Honmachi, present-day Chungmu-ro.