It's the world's largest celebration of Samuel Beckett's work.
Spokesperson for the festival, Conleath Teevan, says Winona will be reading extracts from some of the Nobel Prize winner's work.
"She'll be doing several readings," he said.
"All actors love Beckett and we're delighted Winona is taking part in the festival. She'll be in the Words Without Acts section.
"Winona and some of the other celebrities will read extracts of Beckett's lesser known prose and they'll chat about them afterwards. Winona is a big, big fan of Beckett's work," he said.
The 41-year-old appeared as Winnie in a 2007 film version of Happy Days and is believed to be extremely excited about heading to Enniskillen.
Winona shot to fame in the late 80s and 90s. She appeared in cult film Heathers, starred in Tim Burton's Beetlejuice; and was directed by legends Francis Ford Coppola (Dracula) and Martin Scorsese (The Age of Innocence).
Winona went on to receive two Oscar nominations and dated heartthrob Johnny Depp – before he started wearing those trilby hats and dated Kate Moss.
Things seemed to fall apart for the star when she was caught shoplifting in 2001, but in the past few years, Winona has been making a slow and steady return.
She gave an arresting performance when she appeared in Black Swan and was Spock's mother in Star Trek but Winona won't be the only highlight of the Enniskillen festival.
There are a host of unusual stagings and art exhibitions inspired by Beckett's work; there'll be readings on boats and planes and an underground staging of Not I in Fermanagh's iconic Marble Arch Caves.