People travelling into Manchester city centre by train can now use the tram network at no extra cost.
Trams run from Victoria and Piccadilly stations
Passengers who catch a train from a station inside Greater Manchester are also able to use their ticket to travel between eight Metrolink stations.
Greater Manchester Passenger Transport Executive (GMPTE) said it wanted to make it as easy as possible for people to travel in the city without a car.
The executive is trying to promote environmentally-friendly transport.
All passengers need to do is show their train ticket to tram inspectors.
The ticket must state "Manchester Ctlz" as the destination.
Metrolink services that can be used for free run between Victoria, Shudehill, Market Street, Mosley Street, St Peter's Square, G-Mex, Piccadilly Gardens and Piccadilly.
GMPTE's service delivery director, Denise Lennox, said: "Metrolink has been a massive success for Manchester and it's important that people coming into the city centre from elsewhere in the county are able to benefit from it.
"That's why it is free for all Greater Manchester rail passengers to travel on the tram to any stop in the city centre zone between Victoria and G-Mex."