A Klingon delicacy of serpent worms (pronounced "gawk"). Connoisseurs of Klingon cuisine claim that gagh is best served very fresh — i.e. live.  But it is sometimes served stewed. Gagh is one of the most popular foods served aboard Klingon warships.

A dish that is legendary well beyond the limits of the Klingon Empire, individuals of other cultures have various levels of appreciation for gagh. Hoshi Sato is probably the first human to see and smell gagh first-hand (while trapped aboard the Klingon Raptor Somraw), and that encounter was quite unpleasant. But by the 24th century, many humans have developed a taste for it, including Will Riker and Jean-Luc Picard. It is one of the dishes Riker enjoyed during his pre-transfer feast to the Klingon cruiser Pagh as part of an officer exchange program. During his "last meal," Riker offered some gagh to Dr. Pulaski and she quickly declined. Later, during Riker's duty onboard the Pagh, Second Officer Karg informed Riker that the worms are best eaten live. Commander Riker made a point about changing attitudes when he bravely tried them out at dinner that night.

Jake Sisko's girlfriend Leanne once ordered gagh — a mistake she didn't want to repeat. On the U.S.S. Voyager, Neelix prepared gagh for visiting Klingon pilgrims in 2377 after studying the Klingon database.

There are at least 51 varieties of gagh, distinguished by the type of worm and the way they are prepared. Each variety of gagh tastes and "feels" different as they are swallowed. For example, Torgud gagh wiggles. Filden gagh squirms. Meshta gagh jumps. Bithool gagh has feet. Wistan gagh is packed in targ blood. Jadzia Dax, before her death, ordered 51 cases of gagh for Martok's birthday party, but when the shipment arrived her successor Ezri could not stomach the thought of all that gagh.