The
River Great Ouse is a river in the
United Kingdom, the longest of
several British rivers called "Ouse". From
Syresham in central
England, the Great Ouse flows into
East Anglia before entering
the Wash, a
bay of the
North Sea. With a course of , mostly flowing north and east, it is the fourth-
longest river in the United Kingdom. The Great Ouse has been historically important for commercial navigation, and for draining the low-lying region through which it flows; its best-known
tributary is
the Cam, which runs through
Cambridge. Its lower course passes through drained
wetlands and
fens and has been extensively modified, or
channelised, to relieve flooding and provide a better route for barge traffic. Though the un-modified river probably changed course regularly after floods, it now enters the Wash after passing through the port of
King's Lynn, south of its earliest-recorded route to the sea.