River Seph

River Seph
Footbridge over the River Seph
Location within North Yorkshire
EtymologySlow Stream
Physical characteristics
Source 
  locationChop Gate
  coordinates54°23′10″N 1°08′27″W / 54.386121°N 1.140853°W / 54.386121; -1.140853
  elevation520 feet (160 m)
MouthSeph Mouth
  coordinates
54°17′28″N 1°08′46″W / 54.291175°N 1.146138°W / 54.291175; -1.146138
Length13 miles (20.5 km)
Basin features
Tributaries 
  leftLedge Beck
Todhill Beck
  rightHollow Bottom Beck
Fangdale Beck

The River Seph (or River Sep) is a tributary of the River Rye (itself a tributary of the River Derwent) in North Yorkshire, England. The river flows for 13 miles (20.5 km) down Bilsdale and meets the Rye near the village of Hawnby. When the surrounding land was owned by Roger de Mowbray, the river was referred to as the Sep.