The International 420 Class Dinghy is a double-handed monohull planing dinghy with centreboard, bermuda rig and centre sheeting. The name describes the overall length of the boat in centimetres (the boat is exactly 4.2 metres long). The hull is fibreglass with internal buoyancy tanks. The 420 is equipped with spinnaker and optional trapeze, making teamwork necessary to sail it well. It has a large sail-area-to-weight ratio, and is designed to plane easily. It can be rigged to be sailed single-handed.
The 420 was designed specifically to be easier to handle than its larger higher-performance cousin, the 470. Both were designed by French engineer Christian Maury, the 420 as a stepping-stone for club and youth sailing to the 470. The 420 is an International class recognized by the International Sailing Federation.