What item does Bilbo first steal from Smaug's lair?

Bilbo first steals a great cup from Smaug’s lair.

The theft occurs after Thorin’s company reaches the secret door into Erebor, the Lonely Mountain. Bilbo is sent inside as the company’s burglar while Smaug sleeps on his vast treasure hoard. He finds a large cup, takes it, and carries it back toward the dwarves.

Smaug immediately notices that the cup is missing. His extraordinary knowledge of the hoard lets him detect the loss, and his anger drives him to search for the intruder. The episode turns Bilbo’s burglary into the first direct provocation of the dragon and sets the danger of the next encounter in motion.

Readers sometimes remember the object simply as a golden cup, since adaptations and summaries describe it that way. “A great cup” is the novel’s canonical wording and is more precise than the other proposed treasures. Bilbo later returns to the lair and learns about the gap in Smaug’s jewel-covered armour, but that discovery happens during a later visit, not the first theft.