The Yridian yak is an animal found on Yridia, the homeworld of the Yridian race.
In 2372, Julian Bashir commented that, after playing Morn in a game of darts, the Lurian couldn't hit a Yridian yak from five paces away. (DS9 episode: "Accession")
Ulrika Corsi owned a sweater made of wool from the Yridian yak. (SCE eBook: Home Fires)