Police believe he was the driver of a van which careered down the Las Ramblas avenue, killing 13 and injuring more than 100 others.
He was killed some 25 miles (40km) west of Barcelona near a sewage treatment works following a tip off.
Abouyaaqoub, wearing a fake explosive belt, is reported to have shouted "Allahu Akbar" ("God is Greatest").
An extensive manhunt was already under way when police closed in on the Subirats area, close to Sant Sadurní d'Anoia.
A petrol station employee spotted Abouyaaqoub and called the police who found him hiding in vineyards.