Longkou (simplified Chinese: 龙口; traditional Chinese: 龍口; pinyin: Lóngkǒu), formerly Huang County (simplified Chinese: 黄县; traditional Chinese: 黃縣; pinyin: Huáng Xiàn), is a port city in northeastern Shandong province, China, facing the Bohai Sea to the north and the Laizhou Bay to the west. Longkou, a county-level city, is administered by the prefecture-level city of Yantai. It is located in the northwest of Jiaodong Peninsula and the south bank of Bohai Bay, adjacent to Penglai District in the east, Qixia City and Zhaoyuan City in the south, Bohai Sea in the west and north, and facing Tianjin and Dalian across the sea. With a total area of 901 square kilometers, the city has jurisdiction over 5 subdistricts, 8 towns and 1 high-tech industrial park.

Longkou has been awarded many honors, such as National Civilized City, China Excellent Tourist City, National Health City, National Green Model City, National Garden City, National Sustainable Development Experimental Zone, National Ecological Protection and Construction Demonstration Zone, and provincial pilot county for transformation and upgrading of scientific development of county economy.

Huang County was the center of the ancient Dongyi state of Lai during China's Zhou dynasty. Under the Qing, it was administered as part of Dengzhou (now Penglai).

Huang County was renamed Longkou in 1986.

There are five subdistricts and eight towns under the city's administration:

Subdistricts:

Towns:

Longkou is a coastal harbour city adjacent to Penglai city and Yantai urban area to the east, linked to Qingdao to the south. Its administrative area (county-level city) covers 893 km² (345 sq mi) and contains a coastline of 68.4 km (42.5 mi).