Cock Beck is a stream in the outlying areas of eastern Leeds, West Yorkshire, England, which runs from its source due to a runoff north-west of Whinmoor, skirting east of Swarcliffe and Manston (where a public house has been named 'The Cock Beck'), past Pendas Fields, Scholes, Barwick-in-Elmet, Aberford, Towton, Stutton, and Tadcaster, where it flows into the River Wharfe.
It is a tributary of the River Wharfe, formerly known as the River Cock or Cock River, having a much larger flow in the past than it does today. Industrial pollution reduced the fish stock, but it has been recovering in the 21st century, aided by work from the Environment Agency. It is believed that this was a defensive construction of the Brigantes against southern tribes and the Romans. The river may have been engineered to increase the barrier.
In the aftermath of the 1461 Battle of Towton remnants of the Lancastrian forces fleeing the victorious Yorkists were forced to try to cross the Cock Beck, having already disposed of most of their arms. Many drowned in the Beck, and soon the survivors were reported to be crossing the Cock Beck on bridges of their fallen comrades. The Cock Beck is now the limit of the heritage protected battlefield site in the Saxton and Towton areas.
During the English Civil War, the Royalists defeated the Parliamentarians under Sir Thomas Fairfax at the Battle of Seacroft Moor in 1643. The ensuing massacre of the Parliamentarians is said to have been of such magnitude that the beck ran crimson with blood.
John Ogilby's 1675 map indicates the major crossing for the Cock was sited along the Tadcaster-Ferrybridge road, however this crossing has no bridge and the steep descent and ascent on either side led to it being abandoned for a new cut, which crosses the Cock Beck further east near its mouth with the River Wharfe.
Hydrology
thumb|left|Cock Beck from the bridge at Towton
The beck flows from west to east across West and North Yorkshire for , draining an area of . It is one of the major tributaries of the River Wharfe, and is one of the last major watercourses to enter the Wharfe before it itself enters the Ouse. The Cock Beck Sluices control the flow of water upstream from the Wharfe into Cock Beck when the Wharfe is in flood. When the water reaches a flooding mark or more than , then the beck backflows upstream to Stutton.