A transom is the flat or slightly curved, transverse structural surface that closes off the stern (rear) of a boat. It connects the two sides of the hull, providing structural integrity, strengthening the stern, and acting as a mounting point for outboards, swim platforms, or boarding ladders.

Key Characteristics and Functions:
Location: The very back (aft end) of the vessel.

Purpose: The transom bears the weight and force of outboard engines, acts as a barrier against following seas, and holds accessories.

Structure: While often vertical, it can be angled (canted) forward or aft. It is typically built from wood, fiberglass, or metal.

Difference from Stern: The stern is the entire rear area of the boat, while the transom is the specific structural panel sealing it.

On many sailboats, the transom is often adorned with the boat's name and may be designed with a transom door or step for water access.