For the similarly-named Klingon, please see Martok.
The Martuk was a Lissepian transport that the USS Rio Grande posed as while under the command of Major Kira and Chief O'Brien when they were hailed by an officer assigned to Post 24 near Cardassia IV. They were able to pull the ruse off by being outside the range for visual communications and by disguising the runabout's power signature. (DS9: "The Homecoming")
According to the script for this episode, the pronunciation for Martuk was "MAR-tuk". [1]
The Star Trek Encyclopedia (4th ed., vol. 2, p. 25) stated that Martuk was a non-existent ship.