As a rule, the minimum age is 21 years. Some rental companies have additional special conditions for tenants under 25 years. In Australia and New Zealand, some rental companies allow rentals from the age of 18 (as long as the drivers have held a driver’s license for at least 6 months).
Further details can be found in the local rental conditions. For most vehicles in Europe, the minimum age of the renter is 21 years. An exception are the vehicles of the Premium Group; here the minimum age is 25 years.