Pupils to re-enact legends in wood.
The specially written production marks the completion of the Meirionnydd Oakwoods Project, which received pounds 2.2m over three years to protect and expand the county's ancient woods.
The event, on June 26, is being organised by Coed Cadw (the Woodland Trust).
"The Oakwoods Project has re-created the woods as they would have been at the time the Mabinogion were written," said Rhydian Roberts, of Coed Cadw.
"So it seemed the natural choice to tell the stories in the same woods to celebrate the end of the project."
Next Thursday children from Ysgol Maenofferen, Blaenau Ffestiniog, will be joined by a drama group from Ysgol y Moelwyn to perform a series of mini-plays in the woods.
Coed Felinrhyd is referred to in the Mabinogion as the place where the two great leaders Gwydion and Pryderi battled to the death.
Minibuses will be leaving Blaenau Ffestiniog on Thursday evening to take people to the production. The first leaves Diffwys Squares Blaenau, at 6.pm, with others at 7pm and 7.30pm. Buses are free but people must book on 01766 832563 or 07760 171174.