A small Klingon colony near the Federation border, where Worf serves as governor in the possible future shown in the Next Generation finale All Good Things...
H'atoria is a minor Klingon colony world close to the border with the Federation. It is mentioned in the anti-time future visited by Picard in All Good Things..., roughly twenty-five years after the main events of The Next Generation.
In that future the Klingons have conquered the Romulan Empire and relations with the Federation are tense. Worf, having left Starfleet and sat for a time on the High Council, has ended up as governor of H'atoria.
Picard, La Forge and Data contact him there seeking permission to cross the border to the Devron system. Worf has no authority to grant it, but Picard's appeal to his honour persuades him to come aboard the USS Pasteur and see them through.