Beijing, previously romanized as Peking, is the capital city of China. With more than 22 million residents, it is the world's most populous national capital city as well as China's second largest city by urban area after Shanghai. It is located in Northern China, and is governed as a municipality under the direct administration of the State Council with 16 urban, suburban, and rural districts. Beijing is mostly surrounded by Hebei Province and neighbors Tianjin to the southeast; together, the three divisions form the Jing-Jin-Ji cluster.

Beijing is a global city and one of the world's leading centres for culture, diplomacy, politics, finance, business and economics, education, research, language, tourism, media, sport, science and technology, transportation, and art. It is home to the headquarters of most of China's largest state-owned companies and houses the largest number of Fortune Global 500 companies in the world, as well as the world's four biggest financial institutions by total assets. It is also a major hub for the national highway, expressway, railway, and high-speed rail networks. For a decade before the COVID-19 pandemic, Beijing Capital International Airport was Asia's busiest airport (2009–2019) and the second busiest airport in the world (2010–2019). In 2020, the Beijing subway was the fourth busiest and second longest in the world. Beijing Daxing International Airport, Beijing's second international airport, is the largest single-structure airport terminal in the world. The city has hosted numerous international and national sporting events, the most notable being the 2008 Summer Olympics and 2008 Summer Paralympics Games. In 2022, Beijing became the first city ever to host both the Summer and Winter Olympics, and also the Summer and Winter Paralympics.

The architecture of Beijing contains elements of both traditional Chinese architecture with modern styles, with one side of the city being modernized and renovated, and the other half still offering traditional hutong districts. Beijing is one of the oldest cities in the world, with recorded history spanning over three millennia. As the last remaining one of the Four Great Ancient Capitals of China, Beijing has been and still is the political center of the country for most of the past eight centuries, and was the largest city in the world by population for much of the second millennium AD. With mountains surrounding the inland city on three sides, in addition to the ancient city fortifications, Beijing was strategically poised and developed to be the residence of the emperor. The city is renowned for its opulent palaces, temples, parks, gardens, tombs, walls and gates. Beijing is considered one of the most well-known tourist destinations in the world. In 2018, Beijing was the second highest earning tourist city in the world after Shanghai. Beijing is home to many national monuments and museums and has eight UNESCO World Heritage Sites—the Forbidden City, Temple of Heaven, Summer Palace, Ming Tombs, Zhoukoudian Peking Man Site, Beijing Central Axis and parts of the Great Wall and the Grand Canal—all of which are popular tourist locations. Siheyuans, the city's traditional housing style, and hutongs, the narrow alleys between siheyuans, are major tourist attractions and are common in urban Beijing.

Beijing's public universities make up more than one-fifth of Double First-Class Construction universities, and many of them consistently rank among the best in the Asia-Pacific and the world, including Tsinghua University, Peking University and UCAS. Beijing CBD is a center for Beijing's economic expansion, with the ongoing or recently completed construction of multiple skyscrapers. Beijing's Zhongguancun area is a world leading center of scientific and technological innovation as well as entrepreneurship. Beijing has been ranked the city with the largest scientific research output by the Nature Index since the list's inception in 2016. Beijing hosts 176 foreign embassies as well as the headquarters of many organizations, including the Asian Infrastructure Investment Bank (AIIB), the Shanghai Cooperation Organisation (SCO), the Silk Road Fund, the Chinese Academy of Sciences, the Chinese Academy of Engineering, the Chinese Academy of Social Sciences, the Central Academy of Fine Arts, the Central Academy of Drama, the Central Conservatory of Music, and the Red Cross Society of China.

Over the past 3,000 years, the city of Beijing has had numerous other names. The name Beijing, which means "Northern Capital" (from the Chinese characters 北 běi for north and 京 jīng for capital), was applied to the city in 1403 during the Ming dynasty to distinguish the city from Nanjing (the "Southern Capital"). The English spelling Beijing is based on the government's official romanization (adopted in the 1980s) of the two characters as they are pronounced in Standard Mandarin. An older English spelling, Peking, was used by Jesuit missionary Martino Martini in a popular atlas published in Amsterdam in 1655. Although Peking is no longer the common name for the city, some of the city's older locations and facilities, such as Beijing Capital International Airport, with the IATA code PEK, and Peking University, still retain the former romanization.

The single Chinese character abbreviation for Beijing is 京, which appears on automobile license plates in the city. The official Latin alphabet abbreviation for Beijing is "BJ".

The earliest traces of human habitation in the Peking municipality were found in the caves of Dragon Bone Hill near the village of Zhoukoudian in Fangshan District, where Peking Man lived. Homo erectus fossils from the caves date to 230,000 to 250,000 years ago. Paleolithic Homo sapiens also lived there more recently, about 27,000 years ago. Archaeologists have found neolithic settlements throughout the municipality, including in Wangfujing, located in central Peking.

The first walled city in Beijing was Jicheng, the capital city of the state of Ji which was built in 1045 BC. Within modern Beijing, Jicheng was located around the present Guang'anmen area in the south of Xicheng District. This settlement was later conquered by the state of Yan and made its capital.