Line 12 may refer to:
Asia Line 12 (Beijing Subway), China Line 12 (Dalian Metro), China Line 12 (Guangzhou Metro), China Line 12 (Hangzhou Metro), China Line 12 (Ningbo Rail Transit), China Line 12 (Shanghai Metro), China Line 12 (Shenzhen Metro), China Line 12 (Wuhan Metro), China Line 12 (Mumbai Metro), India Putrajaya line, or Line 12, Malaysia Toei Ōedo Line, originally Line 12, Tokyo, Japan
Europe Line 12 (Barcelona Metro), a shuttle train on the Barcelona–Vallès Line, Spain Line 12 (Madrid Metro), Spain Line 12 (Moscow Metro), Russia Paris Metro Line 12, France S12 (ZVV), Zurich, Switzerland
North America 12 (BMT rapid transit service), New York City, US (defunct) Mexico City Metro Line 12, Mexico Saint-Jérôme line, also designated as line 12, a commuter rail service in Greater Montreal, Quebec
South America Line 12 (CPTM), São Paulo, Brazil
See also List of public transport routes numbered 12