Are there any games on gog that are based on Irish mythology? Genre is not important.

Folkore (PS3)

trailer: https://www.youtube.com/watch?v=Cys_INMFt4w

coughongogcough

The Quiet Man in the form of Barry Fitzgerald as Michaeleen Oge Flynn

Not specifically Irish but Celtic mythological elements are present/recycled in:

Kingdoms of Amalur: Re-Reckoning
Drova: Forsaken Kin
Hellblade: Senua's Sacrifice

The Mystery of the Druids
Barrow Hill: The Dark Path
Barrow Hill: Curse of the Ancient Circle
Rhiannon: Curse of the Four Branches

The Bard's Tale
Pillars of Eternity

A level in Tomb Raider Chronicles iirc

There's leprechauns and pots of gold to be found in Heroes of Might and Magic 4

If your request weren't specifically about "games on GOG"...there would be a few more.

Nioh (PS4, Steam):
Blurb: "Nioh does something quite incredible that seemingly no other game does, including those that utilize Celtic mythology, and that is include the actual Irish language.
Nioh is an oddity of a game, taking a historical British sailor and making him Irish, taking his formal position as a samurai into a more literal combat role, and making him face yokai of Japanese myth.
It's a lot."

Clan O'Conall and the Crown of the Stag (Switch, Steam)
Blurb: "The game is based on Celtic mythology from the first millennium, taking place in Hibernia.
The player controls one of the three O'Conall siblings, Haggish, Kilcannon, or Clakshot.
Chief Arden was kidnapped by Caoranach, mother of demons, who also stole the Crown of the Stag in order to incite a war between mortals and the Fae, or fairy-folk."

And then there's also:
https://en.wikipedia.org/wiki/Category%3Video_games_based_on_Celtic_mythology
(I know, I know...Celtic doesn't mean Irish, but...beggars can't be choosers, huh!?)

Should you ever come in the taste for Slavic mythology I can heartily suggest the Thea games.

https://www.gog.com/en/game/thea_the_awakening
https://www.gog.com/en/game/thea_2_the_shattering

Tir Na Nog (you're playing as Cuchulainn) and Dun Darach. Old ZX Spectrum games by Gargoyle Games.

Maid of Sker, more Welsh than Irish, but still...

I remember one i played a couple of decades ago , " Celtic Tales - Balor of the Evil Eye ", it was based on Irish myths, the story was taking place in Ireland.
It was very good in its time but surprisingly it's not on gog : https://www.gog.com/wishlist/games/celtic_tales_balor_of_the_evil_eye

Thanks everybody! I now have more games to check out. Some will go straight to the wishlist, but for some I will have to go beyond GOG. :) I believe Irish mythology is Celtic. And so is Gaulish. Irish = Celtic, Gaulish = Celtic, but Irish ≠ Gaulish.

By the way, where is your avatar from?

I am a Slav, so I am familiar with it and the Thea games. I would say after The Witcher gained popularity we are getting
more and more games that are inspired by Slavic myths, which is nice.

It's from the old French comic: "Les Krostons" (1968 - 1983).