• A3 is a standard paper size, defined by the international standard ISO 216.
• The A3 road is a trunk road in Southern England, connecting London to Portsmouth.
• A3 (Switzerland) is an expressway in Switzerland.
• A3 is also a car from Audi, see Audi A3.
• A3 is the United States alias of the London band Alabama 3 (having been sued by Alabama).
• The A3 Highway is an italian toll-free highway.
• The A3 (rocket)