Line 9 or 9 Line may refer to:
Asia China Line 9 (Beijing Subway), a subway line in Beijing Line 9 (Chengdu Metro), a metro line in Chengdu, Sichuan Line 9 (Chongqing Rail Transit), a metro line in Chongqing Line 9 (Guangzhou Metro), a metro line in Guangzhou, Guangdong Line 9 (Hangzhou Metro), a metro line in Hangzhou, Zhejiang Line 9 (Shanghai Metro), a metro line in Shanghai Line 9 (Shenyang Metro), a metro line in Shenyang, Liaoning Line 9 (Shenzhen Metro), a metro line in Shenzhen, Guangdong Line 9 (Tianjin Metro), a metro line in Tianjin Line 9 (Xi'an Metro), a metro line in Xi'an, Shaanxi
India Line 9 (Mumbai Metro)
Malaysia Kajang line, called Line 9 at route map
Philippines Metro Manila Subway Line 9, Metro Manila
South Korea Seoul Subway Line 9, a subway line in Seoul
Europe France Paris Metro Line 9, one of 16 metro lines in Paris
Italy Line 9 (Naples Metro), rapid transit railway line that forms part of the Metropolitana di Napoli
Russia Line 9 (Moscow Metro), a metro line of the Moscow Metro, Moscow
Spain Barcelona Metro line 9, one of the two branches of the Barcelona metro extension line 9/10 Line 9 (Madrid Metro)
North America Mexico Mexico City Metro Line 9, a rapid transit line in Mexico City
United States 9 (New York City Subway service) Route 9 (Baltimore), a bus route 9 (Los Angeles Railway)
South America Brazil Line 9 (CPTM), São Paulo
Chile Santiago Metro Line 9, a planned railway line
Oceania Australia T9 Northern Line, Sydney Trains service
See also List of public transport routes numbered 9