Lianyungang (simplified Chinese: 连云港; traditional Chinese: 連雲港; pinyin: Liányúngǎng) is a prefecture-level city in northeastern Jiangsu province, China. It borders Yancheng to its southeast, Huai'an and Suqian to its south, Xuzhou to its southwest, and the province of Shandong to its north. Its name derives from Lian Island, the largest island in Jiangsu which lies off its coastline, and Yuntai Mountain, the highest peak in Jiangsu, a few miles from the city center, and the fact that it is a port. The name can be literally translated as the Port Connecting the Clouds.

Lianyungang was home to 4.65 million inhabitants as of the 2020 census whom 1,210,767 lived in the built-up (or metro) area made of Haizhou and Lianyun counties. Lianyungang was known in the West as Haichow (Postal romanization), which means the City of Sea. Haichow was opened to foreign trade by the Qing imperial government in 1905.

Lianyungang is between 118°24' and 119°48' east longitude and 34°11' and 35°07' north latitude. Lianyungang covers an area of 7,777 km² (3,003 sq mi). Lianyungang City is located in the central coastal area of China, in the northeastern part of Jiangsu Province. It borders the Yellow Sea in the east, faces North Korea, South Korea and Japan across the sea, borders Rizhao City in Shandong Province in the north, Linyi City in Shandong Province and Xuzhou City in Jiangsu Province in the west, and Suqian City, Huai'an City and Yancheng City in Jiangsu Province in the south.

The prefecture-level city of Lianyungang administers six county-level divisions, including three districts and three counties.

Lianyungang is one of the first 14 Chinese coastal cities opening to the outside world and a rising center of industry, foreign trade, and tourism in east China. It is the eastern terminus of the New Eurasian Land Bridge and the proposed Northern East West Freight Corridor. The New Eurasia Continental Landbridge continue by land, connecting Lianyungang with over 40 countries and regions in Europe, South Asia and the Middle East by railway networks.

The Lianyun-Port, in the center of the coast, links eastern sea routes with western land routes. Japan and South Korea in the east can be reached economically and conveniently from Lianyungang. Near the port, the Tianwan Nuclear Power Plant is one of the biggest nuclear power plants in China, with two operational units and six more planned. Lianyungang is also rich in mineral resources. Donghai County has 70% of the national reserve of natural crystal, and is manufacturing 80% of China's crystal products.

The Chinese government has stated its intention to build an economic belt along the New Eurasia Continental Landbridge in "the Ninth Five-Year Plan of the National Economy and Social Development and the Long-range Goal for the Year 2010." On "China's 21st Century Agenda", Lianyungang is to be developed into an international seaport linking countries on the Pacific rim with those in Central Asia. In the "National Ocean Development Plan" it is listed as one of three special development zones.

Lianyungang Economic & Technological Development Zone was approved by the State Council as one of the first batch of state-level development zones in December 1984. It is in the eastern new seashore urban area of Liangyungang City. The distance to the nearest airport, Liangyungang Airport is 10–20 km (6.2–12.4 mi) and the distance to the nearest highway G310 is 10–20 km (6.2–12.4 mi). Lianyungang port is 20–50 km (12–31 mi).