A bin bag, rubbish bag (British English), garbage bag, bin liner, trash bag (American English) or refuse sack is a disposable bag used to contain solid waste. Such bags are useful to line the insides of waste containers to prevent the insides of the receptacle from becoming coated in waste material. Most bags today are made out of plastic, and are typically black, white, or green in color.

Plastic bags are a widely used, convenient, and sanitary way of handling garbage. Plastic garbage bags are fairly lightweight and are particularly useful for messy or wet rubbish, as is commonly the case with food waste, and are also useful for wrapping up garbage to minimize odor. Plastic bags are often used for lining litter or waste containers or bins. This keeps the container sanitary by avoiding container contact with the garbage. After the bag in the container is filled with litter, the bag can be pulled out by its edges, closed, and tied with minimal contact with the waste matter.

Garbage bags were invented by Canadians Harry Wasylyk, Larry Hansen and Frank Plomp in 1950. In a special on CBC Television, green garbage bags (first bin bags in Canada) ranked 36th among the top 50 Canadian inventions. Black plastic bags were introduced in 1950 as star sealed bags. The first bags in the United States were green and black, rather than the now-common white and clear. Flat-sealed bags first appeared in 1959. In the 1960s, the white bin bags were introduced. Two-ply (Heavy Duty) bags were introduced in 1974, with 3 ply bags following in 1980.

Plastic bags can be incinerated with their contents in appropriate facilities for waste-to-energy conversion. They are stable and benign in sanitary landfills; some are degradable under specified conditions.