Plastic shopping bags, carrier bags, or plastic grocery bags are a type of plastic bag used as shopping bags and made from various kinds of plastic. In use by consumers worldwide since the 1960s, these bags are sometimes called single-use bags, referring to carrying items from a store to a home. However, reuse for storage or trash is common, and modern plastic shopping bags are increasingly recyclable or biodegradable. In recent decades, numerous countries have introduced legislation restricting the sale of plastic bags, in a bid to reduce littering and plastic pollution.
Some reusable shopping bags are made of plastic film, fibers, or fabric.
American and European patent applications relating to the production of plastic shopping bags can be found dating back to the early 1950's, but these refer to composite constructions with handles fixed to the bag in a secondary manufacturing process. The modern lightweight shopping bag is the invention of Swedish engineer Sten Gustaf Thulin. In the early 1960s, Thulin developed a method of forming a simple one-piece bag by folding, welding and die-cutting a flat tube of plastic for the packaging company Celloplast of Norrköping, Sweden. Thulin's design produced a simple, strong bag with a high load-carrying capacity, and was patented worldwide by Celloplast in 1965.
Celloplast was a well-established producer of cellulose film and a pioneer in plastics processing. The company's patent position gave it a virtual monopoly on plastic shopping bag production, and the company set up manufacturing plants across Europe and in the US. However, other companies saw the attraction of the bag, too, and the US petrochemicals group Mobil overturned Celloplast's US patent in 1977.