IRUN, a frontier town of northern Spain, in the province of Guipuzcoa, on the left bank of the river Bidasoa. Pop. (193o) 17,670. Irun is the northern terminus of the Spanish Northern railway, and a thriving industrial town, with ironworks, tan-yards, potteries and paper mills. It derives its prosperity from the fact that it is the most important custom-house in Spain for the over land trade with the rest of Europe. Irun is also on the chief
highway for travellers and mails. It is the terminus of some important narrow-gauge mining railways and steam tramways, which place it in communication with the mining districts of Guipuzcoa and Navarre, and with the valuable oak, pine and beech forests of both provinces.