a fortified town of Spain, province of Estremadura, near the left bank of the Guadiana, on the Portuguese frontier, 15 miles S.S.W. of Badajoz. The surrounding country is fertile in corn and wine, and an active trade is carried on in the town. There are several churches and convents, three hospitals, and a poorhouse. Olivenza is strongly fortified, and till 1801 belonged to Portugal. Pop. 6300.