Free wi-fi will be available on First Great Western (FGW) services in the region, the company has announced.
The roll-out on board the high speed train fleet and the Night Riviera sleeper service will begin in May 2014 and conclude by the end of the year.
FGW managing director Mark Hopwood said that the company pledged to increase wi-fi provision across the fleet as part of its new, 23-month franchise.
He said that trials on board had proved a great success.
"We have trialled wi-fi on board our fleet of Class 180 trains, serving the north Cotswolds, and it has been very well received by customers," said Mr Hopwood.
"I am delighted that we are able to extend this free service, and within the next year all high speed and Sleeper fleet customers will be able to read their e-mails, browse the web, or simply catch up with friends while on the move."
Work on fitting the high speed trains with wi-fi will start in May next year, with full completion due by the end of the year.
However, wi-fi on the two daily sleeper services will be available by June 2014.
Wi-fi is currently available at a number of FGW stations through the public provider The Cloud.
The service on board has been rolled out after FGW signed a deal with Nomad Digital.