The name Green Line is used for urban heavy rail and light rail lines on the following public transport systems:

• Boston, Massachusetts (light rail) - Massachusetts Bay Transportation Authority
• Chicago, Illinois (light rail) - Green Line (Chicago Transit Authority)
• Cleveland, Ohio (light rail) - Cleveland Rapid Transit
• Dallas, Texas (light rail) - Trinity Railway Express
• Montreal, Quebec - Montreal Metro
• Los Angeles, California (light rail) - Los Angeles County Metropolitan Transportation Authority
• Seattle, Washington (planned monorail) - Seattle Monorail Project
• Washington, DC - Washington Metro

The name was used by London Transport to describe their express bus services from country areas to central London; these are now operated by a private company, but the name has been retained.