The gold in *Lupin III: Island of Assassins* is the vast treasure amassed by the Tarantula organization through global assassination operations, stored on their secret island base. This fortune fuels the motivations of multiple factions: Lupin and his crew target it for theft, while Tarantula defectors Ellen and Bomber plot to seize it to secure their freedom.

A key deception involves Doc and Gordeau permitting rebels to steal a decoy shipment of fake gold, triggering the island's defense satellite to destroy the rebels' escape ship. The actual gold reserve is later exposed as hidden separately. Gordeau and Doc conspire to eliminate all other assassins—including each other—to claim the treasure solely. Doc ultimately acquires the real gold but plummets into the ocean with it during the final confrontation, losing the treasure forever.

The gold's existence and the conflict it generates directly drive the story's betrayals, shifting alliances, and casualties, culminating in the collapse of the Tarantula organization.