Celebrating its 150th anniversary, the event will now include 11 days of cricket, joining matches against Hampshire, Northamptonshire, Warwickshire and Western Storm v South East Stars
National County Wiltshire will face Gloucestershire at this summer's Cheltenham Festival after being added to the schedule.
The 50-over match will take place on Sunday, July 31.
It sees the festival schedule swell to 11 days of action spread across more than two weeks.
Gloucestershire against Hampshire in the LV=Insurance County Championship on July 19-22 kicks off the action.
Western Storm take on South East Stars in the Rachael Heyhoe-Flint Trophy on 23 July, before Gloucestershire's second four-day game against Northamptonshire on July 25-28.
After facing Wiltshire, twice winners of the National Counties Cricket Championship in 1902 and 1909, Warwickshire are the visitors to Cheltenham College in the Royal London One-Day Cup on August 2.
Western Storm are also in action during the festival (Harry Trump/Getty Images)
"For all of our players, members and supporters this will be a great experience and one that we are very appreciative and proud to be a part of," said Wiltshire Cricket managing director Pete Sykes.
"In recent years we have been delighted to develop a close working relationship with Gloucestershire through our talent pathway partnership.
"With that in mind, this fixture provides a further opportunity for the two counties to come together to demonstrate the benefits of a close working relationship as well as to showcase the talent that exists within national counties cricket."
Will Brown, Gloucestershire chief executive, added: "Adding our fixture against Wiltshire to the Cheltenham Cricket Festival is wonderful news for both counties and our supporters in the north of Gloucestershire.
"It will be fantastic to welcome our neighbours to Cheltenham in what will be the 150th anniversary of the longest-running cricket festival in the world.
"We are delighted to now be hosting two weekend fixtures with Western Storm also making a return to the Festival for the first time since 2018."