The Douro valley where Port wine is produced was defined and established as a protected region , or appellation in 1756 . It is the oldest defined and protected wine region in the world . The Douro valley where Port wine is produced was defined and established as a protected region , or appellation in 1756 -- making it the third oldest defined and protected wine region in the world after Chianti ( 1716 ) and Tokaj ( 1730 ) .