The River Greta is a river in Cumbria

Cumbria

Cumbria , is a non-metropolitan county in North West England. The county and Cumbria County Council, its local authority, came into existence in 1974 after the passage of the Local Government Act 1972. Cumbria's largest settlement and county town is Carlisle. It consists of six districts, and in...

, England

England

England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

. It is a tributary

Tributary

A tributary or affluent is a stream or river that flows into a main stem river or a lake. A tributary does not flow directly into a sea or ocean...

 of the River Derwent

River Derwent, Cumbria

The Derwent is a river in the Lake District of the county of Cumbria in the north of England. The name Derwent is derived from a Celtic word for "oak trees"....

 and flows through the town of Keswick

Keswick, Cumbria

Keswick is a market town and civil parish within the Borough of Allerdale in Cumbria, England. It had a population of 4,984, according to the 2001 census, and is situated just north of Derwent Water, and a short distance from Bassenthwaite Lake, both in the Lake District National Park...

.

The source of the river is to be found near to Threlkeld

Threlkeld

Threlkeld is a village and civil parish in the north of the Lake District in Cumbria, England, to the east of Keswick. It lies at the southern foot of Blencathra, one of the more prominent fells in the northern Lake District, and to the north of the River Glenderamackin.Historically a part of...

 at the confluence of the River Glenderamackin

River Glenderamackin

The River Glenderamackin is a river in the county of Cumbria, England.The river rises on Mungrisdale Common and drains much of the eastern and southern sides of Blencathra....

 and St. John's Beck

St. John's Beck

St. John's Beck is a river in the Lake District of Cumbria, England.The beck has its beginning as an outflow of Thirlmere, whence it flows northwards through St. John's in the Vale, towards Threlkeld, where it meets the River Glenderamackin to form the River Greta....

. From thence, the river runs westward, roughly aligned with the former Cockermouth, Keswick and Penrith Railway

Cockermouth, Keswick and Penrith Railway

The Cockermouth, Keswick and Penrith Railway was incorporated by Act of Parliament on 1 August 1861, for a line connecting the town of Cockermouth with the London and North Western Railway West Coast Main Line at Penrith. Arrangements for the use of the stations at either end The Cockermouth,...

 between Keswick and Penrith

Penrith, Cumbria

Penrith was an urban district between 1894 and 1974, when it was merged into Eden District.The authority's area was coterminous with the civil parish of Penrith although when the council was abolished Penrith became an unparished area....

, the course of which is now walkable.

The river subsequently flows through Keswick before joining with the Derwent just after the latter flows out of Derwentwater.

The major tributaries of the Greta are Naddle Beck

Naddle Beck

Naddle Beck is a minor river of Cumbria, England.Rising beneath Dodd Crag, Naddle Beck flows northward to meet the River Greta.The major tributary of Naddle Beck is Shoulthwaite Gill, which drains the eastern side of High Seat and Bleaberry Fell. Mere Gill joins Shoulthwaite Gill beneath an old...

 and Glenderaterra Beck

Glenderaterra Beck

Glenderaterra Beck is a watercourse in the English county of Cumbria.The beck runs from its source on Burnt Horse through the valley between Lonscale Fell and Blencathra to its confluence with the River Greta at Brundholme near Threlkeld....

.