Aínsa is in the heart of the Aragonese Pyrenees and has no rail connection. The nearest train stations are at Huesca (90 km south) and Zaragoza (160 km south). From either city you need a car or a bus.
By car is the practical choice. From Huesca, take the A-138 north through Barbastro and Ainsa — about 90 minutes. From Zaragoza, allow two to two and a half hours via the A-22 to Huesca and then north on the A-138. The road through the Sobrabe comarca is well-maintained and scenic; the final approach to Aínsa from the south is particularly good, with the hilltop old town coming into view above the river confluence.
By bus, Alosa runs a limited service between Huesca and Aínsa, with one or two departures daily depending on the season. The journey takes around two hours. There is no direct bus from Zaragoza; you change at Huesca or Barbastro. The timetable is infrequent enough that a car is strongly recommended for anyone planning to visit Ordesa or the surrounding valleys.
From Aínsa, the A-138 continues north toward Broto and the entrance to Ordesa y Monte Perdido National Park, about 35 km away.