World Rowing U23 Championships is an international rowing regatta organized by FISA (the International Rowing Federation). It is a week-long event for best rowers under 23 year age.
World Rowing U23 Championships Wikipedia
From 1976 the U23 event was organised as the Nations Cup, independently from FISA. In 2002 it became the World Rowing U23 Regatta, before becoming the Championships from 2005.