The Beijing Subway is the rapid transit system of Beijing Municipality that consists of 29 lines including 24 rapid transit lines, two airport rail links, one maglev line and two light rail tram lines, and 524 stations. The rail network extends 879 km (546 mi) across 12 urban and suburban districts of Beijing and into one district of Langfang in neighboring Hebei province. In December 2023, Beijing Subway became the world's longest metro system by route length, surpassing the Shanghai Metro. With 3.8484 billion trips delivered in 2018 (10.544 million trips per day) and single-day ridership record of 13.7538 million set on July 12, 2019, the Beijing Subway was the world's busiest metro system in the years immediately prior to the outbreak of the COVID-19 pandemic.

The Beijing Subway opened in 1971 and is the oldest metro system in China and on the mainland of East Asia. Before the system began its rapid expansion in 2002, the subway had only two lines. The existing network still cannot adequately meet the city's mass transit needs. Beijing Subway's extensive expansion plans call for 998.5 km (620.4 mi) of lines serving a projected 18.5 million trips every day when Phase 2 Construction Plan finished (around 2025). The most recent expansion came into effect on December 15, 2024, with the openings of Line 3 and Line 12 and an extension of the Changping line.

Single-ride fare
The Beijing Subway charges single-ride fare according to trip distance for all lines except the two airport express lines.

Same-station transfers are free on all subway lines except the two Airport Express lines, the Xijiao Line and the Yizhuang T1 Line, which require the purchase of a new fare when transferring to or from those lines.

Fare free riders
Children below 1.3 metres (51 in) in height ride for free when accompanied by a paying adult. Senior citizens over the age of 65, individuals with physical disabilities, retired revolutionary cadres, police and army veterans who had been wounded in action, military personnel and People's Armed Police can ride the subway for free.

Unlimited-rides fare
Since January 20, 2019, riders can purchase unlimited rides fare tickets using the Yitongxing (亿通行; lit. 'One Hundred Million Rides') app on smartphones, which generates a QR code with effective periods of one to seven days.

Previous fare schedules
On December 28, 2014, the Beijing Subway switched from a fixed-fare schedule to the current distance-based fare schedule for all lines except the Capital Airport Express. Prior to the December 28, 2014, fare increase, passengers paid a flat rate of RMB(¥) 2.00 (including unlimited fare-free transfers) for all lines except the Capital Airport Express, which cost ¥25, The flat fare was the lowest among metro systems in China. Before the flat fare schedule was introduced on October 7, 2007, fares ranged from ¥3 to ¥7, depending on the line and number of transfers.

Each station has two to fifteen ticket vending machines. Ticket vending machines on all lines can add credit to Yikatong cards. Single-ride tickets take the form of an RFID-enabled flexible plastic card.