It's not essential if you're only staying in Barcelona, as public transport connects the airport with the city center and it's easy to get around on foot once you're there. However, if you want to explore the Costa Brava, the Costa Dorada, Montserrat, or other parts of Catalonia, a rental car is highly recommended. It gives you the freedom to combine beaches, coves, charming villages, and inland getaways at your own pace, without relying on organised tours or fixed bus timetables.