The new tickets will allow passengers to travel on certain routes two or three days a week and save hundreds of pounds each year.
It comes after the Government set up a public body called Great British Railways (GBR), which sets fares and timetables for services across the country, sells tickets and manages rail infrastructure.
Analysis shows that a commuter who buys a two-day-a-week flexible ticket to travel between York and Leeds, instead of tickets each day, can save over £210 a year.
Commuters travelling two days a week could also save more than £260 travelling from Woking to London, £230 from Liverpool to Manchester, and £170 from Stafford to Birmingham
The paperless flexible tickets, which are on sale now and can be used from June 28, will allow travel on any eight days in a 28-day period.
The Department for Transport said it cannot provide a list of all the routes which flexible tickets can be bought for, but passengers can use an online season ticket calculator.
Tim Wood, interim chief executive of Transport for the North said: "Today’s launch of flexi-tickets is an important step forwards towards rail recovery.
"A rail sector with the agility to respond to passenger needs is essential if we are to encourage sustainable travel and persuade people to move from cars to rail for their commute.
"This initiative needs to be one of a series of measures designed to give value for money and to engage people we might otherwise lose from the railway. A discounted flexible ticket offering is clearly a move in the right direction."
The introduction of flexible tickets comes amid changing travel patterns due to the coronavirus pandemic.An increase in home working has led to a huge decline in the number of people travelling by rail, particularly those commuting five days a week.
Transport Secretary Grant Shapps said: “Our railways work best when they are reliable, rapid and affordable.
“As we kickstart the biggest reforms to our railways in a generation, flexible season tickets are the first step. They give us greater freedom and choice about how we travel, simpler ticketing and a fairer fare.
“With a season ticket calculator to see which option works best for you, and a book with confidence guarantee to make journeys stress-free, the future of fares is flexible.”
Rail franchises were effectively ended when the Government took over the financial liabilities of operators in March 2020 to keep services running amid the collapse in demand caused by the coronavirus pandemic, at a cost of £12bn.
The emergency agreements will be replaced by passenger service contracts, with GBR contracting private firms to operate trains.