Sardines also have to be processed in the county for the designation
Only sardines produced in Cornwall are to be allowed to be called Cornish sardines after receiving European Union protected status.
The Protected Food Name (PFN) status will mean the description will be recognised across the EU in the same way as Cornish clotted cream.
Only sardines which are caught, landed and processed in the county can have the description.
Fish producers and ministers said the move would protect fish quality.
The sardine is the 40th food in the UK to be granted such protection food under the PFN programme.
The scheme legally protects the name of foods on the basis of links to specific areas, or the use of traditional recipes, to prevent imitation products undermining their market.
Others protected foods include: Stilton Cheese, West Country Cheddar, the Isle of Man's Loaghtan lamb, plus Melton Mowbray pork pies.
Nick Howell, chairman of the Cornish Sardine Association, said the move would allow the county to protect the brand and quality.
He said: "It's one of the main stocks that Cornwall's had for hundreds of years.
"A Cornish sardine now has to be caught within the six-mile (10km) coastline limit, landed in Cornwall, and primary processed here, such as being, gutted, filleted or frozen.
"It's a product we should be proud of. We can use it as a brand name, register it as a trademark and get grants from the European Union to help promote the name."
Food, farming and environment minster Jim Fitzpatrick said the status was a "great thing for producers and consumers".
He said: "The consumer can have greater reassurance about what they're buying, that they're actually getting the product.
"It's also a win-win for producers because it prevents anybody else from imitating Cornish sardines."