Gaywood River (sometimes known as the River Gay or River Gaywood or, in King's Lynn, as the Fisher Fleet) is a tributary of the River Great Ouse in the west of the county of Norfolk. Its source is 11 metres above sea level, northwest of the village of Gayton in Derby Fen, Map Reference TF 705 209. It runs for 6.7 miles (10.8 km) to its outflow into the River Great Ouse in the town of King's Lynn.