The Great Chamber of Thrór was the hall of feasting and council in the mountain-realm of the Lonely Mountain.
When Thorin and Company came upon the chamber in TA 2941 its great doors were half burnt and hanging twisted upon their hinges. The floor of the room was filled with rotting tables, overturned chairs and benches, flagons, bowls, broken drinking horns, skulls, and bones, all covered with dust. Far above came a glimmer of light from unseen openings. The light grew brighter at the further end where the company found the birth-place of the River Running, which was but a short distance from the entrance to the mountain.
The Great Chamber was probably named after Thrór after he became king in TA 2589. Its ruined state testifies that it was one of the scenes of destruction during the Sack of Erebor in TA 2770.