The 'Umbrella' hitmaker will take to the stage 24 hours after the Open'er Festival in Gdynia officially finishes to perform a bonus set.
Fans with a ticket to the four-day event will be permitted to return to the site to watch the 24-year-old singer's gig for free, reported Daily Star.
The Open'er Festival at Gdynia-Kosakowo airfield runs from July 3-6 and will feature headline sets from Blur, Kings of Leon, Arctic Monkeys, and Queens of the Stone Age.
Rihanna will perform at the venue on July 7 as a nod to her recent seventh album Unapologetic, which she promoted with her 777 Tour, playing seven shows in seven countries over seven days.
"Rihanna - yes, Rihanna! - will perform in Poland on 7.7.2013! The artist will give a special performance in Gdynia, the day after Open'er Festival, and the great news is you get to go to that show too if you have a full 4-day festival ticket," her representative said.