The Igo sector is a sector of space.
In early 2369, the USS Yosemite was damaged here while investigating a plasma streamer. At about the same time, two Ferengi freighters were apparently destroyed in the sector by the Cardassians. These two incidents made some at Starfleet believe that the Cardassians would try to annex the Igo sector. (TNG: "Realm of Fear")