Trailer coupler lock with interchangeable adapter

A trailer coupler lock comprising:

• a shell, the shell including a front, a back, a bottom and a top,
• a cove formed in the back of the shell, the cove comprising a concave recess into which a receptacle portion of a coupler may be received,
• an adapter engagement slot formed in the back of the shell at the cove, and
• a first channel extending from the bottom of the shell to the cove;
• and
• an adapter removably received in the adapter engagement slot, the adapter including
• a base with a hole that aligns with the first channel when the adapter is received in the engagement slot, and
• a coupler flange engagement slot;
• and
• a receptacle engaging device, the receptacle engaging device being movable in the first channel from an unlocked position to a locked position, and in the locked position a portion of the receptacle engaging device extending through the hole in the base of the adapter into the cove, and in the unlocked position the receptacle engaging device not extending into the hole in the base of the adapter and not extending into the cove.