The Tavy is a river

River

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

 on Dartmoor

Dartmoor

Dartmoor is an area of moorland in south Devon, England. Protected by National Park status, it covers .The granite upland dates from the Carboniferous period of geological history. The moorland is capped with many exposed granite hilltops known as tors, providing habitats for Dartmoor wildlife. The...

, Devon

Devon

Devon is a large county in southwestern England. The county is sometimes referred to as Devonshire, although the term is rarely used inside the county itself as the county has never been officially "shired", it often indicates a traditional or historical context.The county shares borders with...

, 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...

. The name derives from the Brythonic

Brythonic languages

The Brythonic or Brittonic languages form one of the two branches of the Insular Celtic language family, the other being Goidelic. The name Brythonic was derived by Welsh Celticist John Rhys from the Welsh word Brython, meaning an indigenous Briton as opposed to an Anglo-Saxon or Gael...

 root "Taff", the original meaning of which has now been lost. It has given its name to the town of Tavistock and the villages of Mary Tavy

Mary Tavy

Mary Tavy is a village with a population of around 600, located four miles north of Tavistock in Devon in south-west England; it is named after the River Tavy. It used to be home to the world's largest copper mine Wheal Friendship, as well as a number of lead and tin mines. It borders Dartmoor...

 and Peter Tavy

Peter Tavy

Peter Tavy is a village 3 miles along the A386, North-East of Tavistock, Devon, England; it is named after the River Tavy. St Peter's Parish Church is largely built of granite and has a buttressed west tower....

.
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 Tamar

River Tamar

The Tamar is a river in South West England, that forms most of the border between Devon and Cornwall . It is one of several British rivers whose ancient name is assumed to be derived from a prehistoric river word apparently meaning "dark flowing" and which it shares with the River Thames.The...

 and has as its own tributaries:

• Collybrooke
  Collybrooke
  The Collybrooke or Colly Brook is a brook on Dartmoor in Devon, England. It is a tributary of the River Tavy.-See also:*Rivers of the United Kingdom...
  
  
• River Burn
  River Burn, Devon
  The Burn is a river on Dartmoor, Devon, England.It is a tributary of the River Tavy.-See also:*Rivers of the United Kingdom...
  
  
• River Wallabrooke
  River Wallabrooke
  The Wallabrooke is a river on Dartmoor, Devon, England.It is a tributary of the River Tavy.-See also:*Rivers of the United Kingdom...
  
  
• River Lumburn
  River Lumburn
  The Lumburn is a river on Dartmoor, Devon, England.It is a tributary of the River Tavy.-See also:*Rivers of the United Kingdom...
  
  
• River Walkham
  River Walkham
  The Walkham is a river whose source is on Dartmoor, Devon, England. Flowing under Merivale and Huckworthy Bridges, the river reaches Horrabridge. About three miles further on, by a footbridge on the West Devon Way, it joins the River Tavy.-See also:...
  
  

At Tavistock it feeds a canal running to Morwellham Quay

Morwellham Quay

Morwellham Quay is a historic river port in Devon, England that developed to support the local mines. The port had its peak in the Victorian era and is now run as a tourist attraction and museum...

.

Its mouth it is crossed by the Tavy Bridge

Tavy Bridge

Tavy Bridge is a railway bridge across the mouth of the River Tavy just east of its confluence with the River Tamar. It was built c1890 by the Plymouth, Devonport and South Western Junction Railway to carry the line from St Budeaux to Bere Alston, now part of the Tamar Valley Line.-Structure:The...

 which carries the Tamar Valley railway line

Tamar Valley Line

The Tamar Valley Line is a railway line from Devonport in Plymouth Devon, to Gunnislake in Cornwall, United Kingdom. The line follows the River Tamar for much of its route.-History:...

.

Navigation

The river is navigable inland as far as Lopwell

Lopwell

Lopwell is a site of natural beauty situated at the upper tidal mark on the River Tavy, 3 miles from north Plymouth and 7 miles from Tavistock, Devon, England....

, about a 9 miles (14.5 km) journey from North Corner Quay at Devonport

Devonport, Devon

Devonport, formerly named Plymouth Dock or just Dock, is a district of Plymouth in the English county of Devon, although it was, at one time, the more important settlement. It became a county borough in 1889...

, and river transport was an important feature of the local farming, mining, tourism and forestry economies.