Passengers in London can now use Android Pay on their mobile phones to travel on the Tube, buses, trams and most National Rail services.
It follows the wider UK launch of the payment system on Wednesday.
The new payment app, developed by Google, supports MasterCard and Visa credit and debit cards from many of the UK's major financial institutions.
Android pay can be used across London
To use Android Pay, customers with a suitable phone download the app and link it to their bank card. As with Oyster or contactless payment cards, they then touch in and out with the top half of their phone on the yellow card reader at a station, or touch in only on a bus or at a tram stop.
As with existing methods, Transport for London (TfL) calculates the best fare for each day or week.
Shashi Verma, chief technology officer and director of customer experience at TfL said: `It's great to see another mobile ticketing option introduced into the market. Android is a popular mobile operating system and we have been working closely with Google to ensure that Android Pay is fully incorporated into the Capital's transport network.
`Contactless payments have been a huge success with more than 400 million contactless journeys made already across all TfL and most National Rail services in London, using cards from over 80 countries. As more people see the benefits of this quick and easy to use technology, we're confident the number will increase even more.'
TfL said it is the first transport organisation in the world to accept Android Pay as a method of ticketing. One in 10 contactless transactions in the UK are made on its network, making TfL one of the largest contactless merchants worldwide.
Around a third of all pay-as-you-go journeys in London are now made using contactless payments.