Cijin District (Chinese: 旗津區; Hanyu Pinyin: Qíjīn Qū; Tongyong Pinyin: Cíjin Cyu; Wade–Giles: Chʻi²-chin¹ Chʻü¹; Pe̍h-ōe-jī: Kî-tin-khu) is a district of Kaohsiung City, Taiwan, covering Cijin Island (旗津島) and islands in the South China Sea. It is the second smallest district in Kaohsiung City after Yancheng District, with an area of 1.4639 square kilometers, or 0.5652 square miles. It has a population of 26,282 as of October 2023, making it the 26th most populated district in Kaohsiung, with a population density of 18,414 people per square kilometer, or 47,692 people per square mile.

Cijin forms the original core of the Kaohsiung, which was established by the fisherman Hsu Ah-hua (徐阿華) in the mid-17th century. He realized the attractiveness of the location when he was forced to seek shelter from a typhoon in the Taiwan Strait and returned with settlers from the Hung, Wang, Tsai, Lee, Pai, and Pan families and an idol of the Chinese sea goddess Ma-tsu. This was housed in a bamboo and thatch structure that formed the first Cijin Tianhou Temple. The town grew up around the temple grounds.

HMS Reynard was wrecked near Pratas Island on May 31, 1851.

Cijin Island was once connected to the mainland at the southern tip, but in 1967, this link was severed to create a second entry point to the Port of Kaohsiung. Currently Cijin Island is connect to the mainland via tunnel, thus the island is not valid for Offshore Islands Development Act.

Cijin Island is 8.5 km (5.3 mi) long with an average width of 400 m (1,300 ft).

Two islands and one reef in the South China Sea are administered by Kaohsiung City as part of the districts Zhongxing Village:

The district consists of Cisia (Qixia), Yongan, Jhensing (Zhenxing), Ciai, Fuxing, Zhonghua, Shijian, Beishan, Nanshan, Shangzhu, Zhongzhou, Anshun and Jhongsing (Zhongxing) Villages.

The councilor for Cijin District in the Kaohsiung City Council is Lee Chiao-ju.