Dalian () is a major sub-provincial port city in Liaoning province, People's Republic of China, and is Liaoning's second largest city (after the provincial capital Shenyang) and the third-most populous city of Northeast China. Located on the southern tip of Liaodong peninsula, it is the southernmost city in both Liaoning and the entire Northeast. Dalian borders the prefectural cities of Yingkou and Anshan to the north and Dandong to the northeast, and also shares maritime boundaries with Qinhuangdao and Huludao across the Liaodong Bay to west and northwest, Yantai and Weihai on the Shandong peninsula across the Bohai Strait to the south, and North Korea across the Korea Bay to the east.

As of the 2020 census, its total population was 7,450,785 inhabitants whom 5,106,719 lived in the built-up (or metro) area made of 6 out of 7 urban districts, Pulandian District not being conurbated yet.

Today a financial, shipping, and logistics center for East Asia, Dalian has a significant history of being used by foreign powers for its ports. Dalian was previously known as "Dalniy" (Russian: Дальний; Dal'nii), "Dairen" (Japanese: 大連), and "Lüda" or "Luta" (Chinese: 旅大; pinyin: Lǚdà). The city used to be better known as "Port Arthur" and "Ryojun" (Japanese: 旅順) from the original Port Arthur, now the city's Lüshunkou district.

In 2016, Dalian ranked 48th in the Global Financial Centres Index. In 2012, Dalian ranked 82nd in the Global City Competitiveness Index. In 2006, Dalian was named China's most livable city by China Daily. It is now a "Beta - Global City" according to the Globalization and World Cities Research Network. The large amount of port traffic makes Dalian a Large-Port Metropolis.

Dalian is one of the top 50 science cities in the world by scientific research as tracked by the Nature Index, ranking 49th in the world as of 2022. The city is home to several major universities, notably Dalian University of Technology and Dalian Maritime University, members of China's prestigious universities in the Project 211, and the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences.