Shanghai (; Chinese: , Shanghainese: Zaon6he5 [z.h] (listen), Standard Mandarin pronunciation: [.x] (listen)) is one of the four direct-administered municipalities of the People's Republic of China (PRC). The city is located on the southern estuary of the Yangtze River, with the Huangpu River flowing through it. With a population of 24.89 million as of 2021, Shanghai is the most populous urban area in China with 39,300,000 inhabitants living in the Shanghai metropolitan area, the second most populous city proper in the world and the only city in East Asia with a GDP greater than its corresponding capital. As of 2018, the Greater Shanghai metropolitan area was estimated to produce a gross metropolitan product (nominal) of nearly 9.1 trillion RMB ($1.33 trillion), exceeding that of Mexico with GDP of $1.22 trillion, the 15th largest in the world. Shanghai is one of the world's major centers for finance, business and economics, research, education, science and technology, manufacturing, tourism, culture, dining, art, fashion, sports, and transportation, and the Port of Shanghai is the world's busiest container port. In 2019, the Shanghai Pudong International Airport was one of the world's 10 busiest airports by passenger traffic, and one of the two international airports serving the Shanghai metropolitan area, the other one being the Shanghai Hongqiao International Airport.

Originally a fishing village and market town, Shanghai grew in importance in the 19th century due to both domestic and foreign trade and its favorable port location. The city was one of five treaty ports forced to open to European trade after the First Opium War. The Shanghai International Settlement and the French Concession were subsequently established. The city then flourished, becoming a primary commercial and financial hub of Asia in the 1930s. During the Second Sino-Japanese War, the city was the site of the major Battle of Shanghai. After the war, with the communists takeover of the mainland in 1949, trade was limited to other socialist countries and the city's global influence declined. Despite this, modern trade in the newly established PRC began in the late 1940s/early 1950s, and Shanghai officially became one of the biggest and most important cities among socialist states before the economic reform in 1978.

By the 1990s, economic reforms introduced by Deng Xiaoping a decade earlier resulted in an intense redevelopment of the city, especially the Pudong New Area, aiding the return of finance and foreign investment. The city has since re-emerged as a hub for international trade and finance; it is the home of the Shanghai Stock Exchange, one of the largest stock exchanges in the world by market capitalization and the Shanghai Free-Trade Zone, the first free-trade zone in mainland China. As of 2020, Shanghai was classified as an Alpha+ (global first-tier) city by the GaWC and ranked as having the 3rd most competitive and largest financial center in the world behind New York City and London. It has the largest metro network of any city in the world, the fifth-highest number of billionaires of any city in the world, the fifth-largest number of skyscrapers of any city in the world, the fifth-most Fortune Global 500 headquarters of any city in the world within its city limits, the fifth-largest scientific research output of any city in the world, and highly ranked educational institutions including Fudan, Shanghai Jiao Tong, Tongji, East China Normal, Shanghai, Donghua, ShanghaiTech, Shanghai University of Finance and Economics, East China University of Science and Technology, and University of Shanghai for Science and Technology.

Shanghai has been described as the "showpiece" of the booming economy of China. Featuring several architectural styles such as Art Deco and shikumen, the city is renowned for its Lujiazui skyline, museums and historic buildings including the City God Temple, Yu Garden, the China Pavilion and buildings along the Bund, which includes Oriental Pearl TV Tower. Shanghai is also known for its sugary cuisine, distinctive local language and vibrant international flair. As an important international city, Shanghai is the seat of the New Development Bank, a multilateral development bank established by the BRICS states and the city hosts more than 75 foreign representatives, the second highest after Beijing and numerous national and international events every year, such as Shanghai Fashion Week, the Chinese Grand Prix and ChinaJoy. Shanghai is the highest earning tourist city in the world, with the seventh most five-star hotels in the world, and the third tallest building in the world, the Shanghai Tower. In 2018, Shanghai hosted the first China International Import Expo (CIIE), the world's first import-themed national-level expo. Shanghai joined the UNESCO Global Network of Learning Cities in 2019.

On 31 December 2014, a deadly crush occurred in Shanghai, near Chen Yi Square on the Bund, where around 300,000 people had gathered for the new year celebration. 36 people were killed and another 49 were injured, 13 seriously.