Donatu V, known in Klingonese as Dona'tu vagh, was the inhabited fifth planet of the Donatu system. This system was located in the Beta Quadrant. The system was located in the same quadrant as Sherman's Planet, Deep Space Station K-7, and an unidentified Klingon outpost. (TOS: "The Trouble with Tribbles"; PIC: "Maps and Legends")
Ownership of Donatu V, as well as the rest of the surrounding region, was disputed between the United Federation of Planets and the Klingon Empire from the point of first contact through the mid-2250s.
The Battle of Donatu V, one of the few brush wars fought between the two powers during the Federation-Klingon Cold War, was fought here in 2245. The battle was inconclusive. (TOS: "The Trouble with Tribbles")
In 2374, during the Dominion War, the Jem'Hadar had destroyed three convoys destined for this planet. For the fourth convoy, the IKS Rotarran was ordered to escort three cargo vessels, which included the IKS Par'tok, to Donatu V. The mission was a success. (DS9: "Sons and Daughters")
This planet was only mentioned in dialogue.
According to Star Trek: Star Charts (pp. 60, 64) and Stellar Cartography: The Starfleet Reference Library ("Federation Historical Highlights, 2161-2385"), the Donatu system was located in the Beta Quadrant. The system's primary was a G-class star.