Theta-class AT-AT barge was one of several dropships used by the Galactic Empire.
Though it was similar in general shape to the Y-85 Titan dropship, the AT-AT barge was far smaller and had a dark blue or light beige color. The AT-AT barge could only carry a single AT-AT walker and was primarily used aboard smaller capital ships, like Star Destroyers. Because of the barge's limited size, the walker had to be carried with its legs folded and unprepared for immediate combat. Only after being dropped off could the walker extend its legs and enter battle.
The Galactic Empire reluctantly used these, because, like the Y-85 Titan dropship, the Theta-class barge was manufactured by the Incom Corporation.