The Yangtze or Yangzi (English: or ; simplified Chinese: 长江; traditional Chinese: 長江; pinyin: Cháng Jiāng; lit. 'long river') is the longest river in Eurasia, the third-longest in the world, and the longest in the world to flow entirely within one country. It rises at Jari Hill in the Tanggula Mountains of the Tibetan Plateau and flows 6,300 km (3,900 mi) in a generally easterly direction to the East China Sea. It is the seventh-largest river by discharge volume in the world. Its drainage basin comprises one-fifth of the land area of China, and is home to nearly one-third of the country's population.

The Yangtze has played a major role in the history, culture, and economy of China. For thousands of years, the river has been used for water, irrigation, sanitation, transportation, industry, boundary-marking, and war. The prosperous Yangtze Delta generates as much as 20% of China's GDP. The Three Gorges Dam on the Yangtze is the largest hydro-electric power station in the world that is in use. In mid-2014, the Chinese government announced it was building a multi-tier transport network, comprising railways, roads and airports, to create a new economic belt alongside the river.

The Yangtze flows through a wide array of ecosystems and is habitat to several endemic and threatened species including the Chinese alligator, the narrow-ridged finless porpoise, and also was the home of the now extinct Yangtze river dolphin (or baiji) and Chinese paddlefish, as well as the Yangtze sturgeon, which is extinct in the wild. In recent years, the river has suffered from industrial pollution, plastic pollution, agricultural runoff, siltation, and loss of wetland and lakes, which exacerbates seasonal flooding. Some sections of the river are now protected as nature reserves. A stretch of the upstream Yangtze flowing through deep gorges in western Yunnan is part of the Three Parallel Rivers of Yunnan Protected Areas, a UNESCO World Heritage Site.