They will run between Banbury and Charlbury railway stations and the festival site at Great Tew, near Chipping Norton, from Thursday, July 4, until Monday, July 8.
The service from Banbury, numbered 490, will also call at the town’s bus station.
A number of buses on route CF1 from Charlbury station will run to and from Witney’s Market Square or make connections in Charlbury with X9 buses between Witney and Chipping Norton.
Fares will be £5 single for adults from Banbury and Witney, £4 from Charlbury, or £8 day return.
For timetable information, see cornburyfestival.com