Irtok was a star system near Ferenginar.

When, in 2374, Rom floated the possibility that the Dominion had conquered Ferenginar, Major Kira Nerys countered that it could not have been taken without first conquering systems like Irtok and Clarus. Misunderstanding this response, Rom assumed Irtok had been taken over by the Dominion, too but, as Worf pointed out moments later, there had been no reports of Dominion activity in or near that system. (DS9: "Profit and Lace")

According to Star Trek: Star Charts ("United Federation of Planets I") and Stellar Cartography: The Starfleet Reference Library ("Federation Historical Highlights, 2161-2385"), the Irtok system was located in the Alpha Quadrant. The system's primary was a G-class star.