San Sebastian airport (EAS) is 22 km away from downtown. There are direct flights to Barcelona and Madrid airports. There is taxi, rent a car and service available .
Biarritz airport (BIQ) is 40 km away. It has several direct connections to French cities and a few abroad. Though not as well connected with the city as San Sebastian or Bilbao airports, there are a few buses per day to San Sebastian.
The Estación del Norte is located at the city center. Trains are operated by Renfe:
Estación del Norte - Pº de Francia
Tf.: +34 943 28 30 89 / +34 943 28 35 99
Good connections from main Spanish cities. More information available here.