Abstract: A device for preventing the theft of a towed vehicle having a towing coupler including a coupler cavity adapted to receive a towing ball. The theft prevention device includes a post sized to be received in the coupler cavity, a frame for supporting the post and a cover hingedly attached to the frame and including a second post projecting therefrom for trapping the hitch with the cavity engaged by the towing post when the cover is in a closed position. The frame and cover include first and second locking plates which lie adjacent one another for engagement by the shackle of a padlock when the cover is in a closed position. The frame and cover further define a closure for sheltering the locking plates and the padlock to prevent tampering with the padlock or locking plates when the cover is in the closed position.