Irun (old Basque for "fortified town" is a town of the Bidasoaldea region in the province of Gipuzkoa in the Basque Autonomous Community, Spain. Nowadays it is widely accepted by the historic researcher community that Irun is the ancient Basque Roman town of Oiasso on account of the vestiges (port, factory, etc.) disclosed lately in the historic nucleus of Irun, while the name itself may have applied to the whole surrounding area.[

One of the biggest towns in Gipuzkoa, its border town situation (it is located on the border between Spain and France, across the Bidasoa river from Hendaye), has made Irun into a commercial and logistic centre, with important railway infrastructure, where the SNCF 1,435 mm (4 ft 8 ½ in) standard gauge rails meet the 1,668 mm (5 ft 5 21/32 in) broad gauge Renfe ones. Currently Irun features a fair ground provided with modern exhibition and telecommunication facilities just at some 100 metres away from the actual borderline at the Santiago Bridge (river Bidasoa).

Irun is part of the conurbation of Txingudi bay with Hondarribia and Hendaye, the town being also involved in the Eurocite Basque Bayonne-San Sebastian.

One of its main festivals is the Alarde de San Marcial, a parade recreating an episode of the Peninsular War, held on every 30 June yearly.