The International 505 is a One-Design high-performance two-person monohull planing sailing dinghy, with spinnaker, utilising a trapeze for the crew.

This sailboat competed in the International Yacht Racing Union (IYRU) selection trials at La Baule, France, in 1953 for a new two-person performance dinghy for the Olympics.

Although the Coronet lost Olympic selection to the Flying Dutchman, in 1954 the Caneton Association of France asked Westell to modify his design to create for them a 5-metre performance dinghy that would be suitable to their needs.

There is a handful of sailmakers that dominate the 505 class: Pinnell & Bax[3] in the UK, Bojsen-Møller[4] in Europe, Glaser[5] and North in the US and Narval in Poland.

Hulls are usually cored with foam, balsa or Nomex to increase stiffness and durability, spars traditionally were manufactured from aluminium alloy, later rule changes have permitted the use of carbon fibre for boom and spinnaker pole.