Girona is compact enough to explore on foot and in any case, it is unlikely that you would want to take a car into the steep, narrow passages of the old town. However, a car is essential for access to the Costa Brava or if your hotel is some distance away.

While it is possible to use public transport to travel to locations outside the city such as towns like Figueres, trains to Girona finish as early as 21:30 and do not run directly to most of the costal towns of the Costa Brava, in which case car hire is essential.

Car rental can be arranged on arrival at the airport, but it is often better to book in advance to ensure you are able to obtain a hire car for your preferred dates.
Girona car hire from ebookers
car hire from easyCar