Donatu V is a planet located near Sherman's Planet and the Federation-Klingon border. Ownership of this planet, as well as the rest of the region, was disputed between the Federation and the Klingon Empire from the point of First Contact through the late 2260s.
The inconclusive 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. (TOS: "The Trouble with Tribbles")
In 2374, during the Dominion War, the IKS Rotarran was ordered to escort a convoy of Klingon freighters, which included the IKS Par'tok, to Donatu V. (DS9: "Sons and Daughters")