Shenzhen, also historically known as Sham Chun, is a major sub-provincial city and one of the special economic zones of China. The city is located on the east bank of the Pearl River estuary on the central coast of southern province of Guangdong, bordering Hong Kong to the south, Dongguan to the north, and Huizhou to the northeast. With a population of 17.56 million as of 2020, Shenzhen is the third most populous city by urban population in China after Shanghai and Beijing. Shenzhen is a global center in technology, research, manufacturing, business and economics, finance, tourism and transportation, and the Port of Shenzhen is the world's fourth busiest container port. Shenzhen is classified as a Large-Port Megacity, the largest type of port-city in the world.Shenzhen roughly follows the administrative boundaries of Bao'an County, which was established since imperial times. The southern portion of Bao'an County was seized by the British after the Opium Wars and became Hong Kong, while the village of Shenzhen was situated on the border. Due to the completion of a train station that was the last stop on the Mainland Chinese section of the railway between Guangzhou and Kowloon, Shenzhen's economy grew and became a market town and later a city by 1979, absorbing Bao'an County for the next decade.
In the early 1980s, economic reforms introduced by Deng Xiaoping resulted in the city becoming the first special economic zone of China due to its close proximity to Hong Kong, attracting foreign direct investment and migrants searching for opportunities. In thirty years, the city's economy and population boomed and has since emerged as a hub for technology, international trade, and finance. It is the home to the Shenzhen Stock Exchange, one of the largest stock exchanges in the world by market capitalization and the Guangdong Free-Trade Zone. Shenzhen is ranked as an Alpha- (global first-tier) city by the Globalization and World Cities Research Network. Its nominal GDP has surpassed neighboring cities of Guangzhou and Hong Kong and is now among the top ten cities with the largest economies in the world. Shenzhen also has the eighth most competitive and largest financial center in the world, the eighth-most Fortune Global 500 headquarters of any city in the world, fifth-highest number of billionaires of any city in the world, the second largest number of skyscrapers of any city in the world, the 28th largest scientific research output of any city in the world, and several notable educational institutions, such as Shenzhen University, Southern University of Science and Technology, and Shenzhen Technology University.
Due to the city being a leading global technology hub, Shenzhen has been dubbed by media China's Silicon Valley. The city's entrepreneurial, innovative, and competitive-based culture has resulted in the city being home to numerous small-time manufacturers or software companies. Several of these firms became large technology corporations such as phone manufacturer Huawei, holding company Tencent, and drone-maker DJI. As an important international city, Shenzhen hosts numerous national and international events every year, such as the 2011 Summer Universiade and the China Hi-Tech Fair. Shenzhen's rapid success has resulted in the Chinese government turning Shenzhen into a model city for other cities in China to follow.