A plastic bag or pouch is a type of flexible packaging made of thin, flexible, plastics film. Plastic bags are used for containing and transporting goods such as foods, produce, powders, ice, chemicals and waste.

Most plastic bags are heat sealed together. Some are bonded with adhesives or are stitched. A press-to-close zipper can be used to open and close the bag many times.

Bags or pouches are a type of packaging for containing frozen food, fresh produce, snack foods, hardware, gardening products, etc. They are often made from a single roll of film on a horizontal or vertical form fill sealing machine.

Several design options and features are available. Some bags have gussets to allow a higher volume of contents. Some have the ability to stand up on a shelf or a refrigerator. Some have easy-opening or reclosable options. Handles are cut into or added onto some.

Bag-In-Box packaging is often used for liquids such as wine and institutional sizes of other liquids.

Plastic bags usually use less material than comparable boxes, cartons, or jars, thus are often considered as "reduced or minimized packaging" . Depending on the construction, plastic bags can be well suited for plastic recycling. They can be incinerated in appropriate facilities for waste-to-energy conversion. They are stable and benign in sanitarylandfills. If disposed of improperly, however, plastic bags can create unsightly litter and harm some types of wildlife.

Bags are also made with carrying handles, hanging holes, tape attachments, security features, etc. Some bags have provisions for easy opening and re-closing. Some bags are sealed and can only be opened by destroying the packaging, providing some tamper-evident capability.

Bags can be made with a variety of plastics films. Polyethylene, of various grades and types, is the most common. Other forms, including laminates and coextrusions can be used when the physical properties are needed.