The ON and later ONS convoys were a series of North Atlantic trade convoys running Outbound from the British Isles to North America during the Atlantic campaign of the Second World War. The ON convoys replaced the earlier OA/OB series of outbound convoys in July 1941 and ran until the end of the campaign in May 1945. They were organized as alternating fast and slow convoys until March 1943, when the ONS series was begun to take over the slow trans-Atlantic traffic, after which all in the ON series were fast.