A golf bag having an improved base is provided. The golf bag is durable, lightweight, comfortable to carry, and easy to use. The base is made of a composite sheet material, preferably a self-reinforced polymer composite sheet material that has been thermoformed. Materials made of thermoplastic polymers such as polyethylene, polypropylene, polyoxymethylene, and polyester can be processed under precise temperature and pressure conditions to form the self-reinforced polymer composite sheet material.