Walmart is the flagship brand name of Walmart Inc.,note the largest discount store chain in the world, headquartered in Bentonville, Arkansas. It operates in the United States, Puerto Rico, Canada, Mexico, Central America, Brazil, Argentina, Africa (under Massmart), the United Kingdom (as ASDA), China, and Japan (as Seiyu and other brands). One of their most notable failed expansions was into Germany, which failed not because Germans dislike the concept per se,note but because others (like Aldi) were cheaper and had a long established customer base. Although highly popular, it is criticized for a number of things, most notably the fact that, at least in the US and Canada, it is vociferously anti-union, with low pay and benefits, even compared to its competitors.
The first Walmart store opened in Rogers, Arkansas in 1962 by founder Sam Walton. Today, it's practically the archetype of the big box development in Suburbia, with over 4,000 stores in the U.S., most of which are Supercenters (a combination between discount store and supermarket). It also operates a sister wholesale club chain, Sam's Club.
The chain has also developed Walmart Express, a smaller version whose main intent is to serve markets too small for a full-sized Walmart while still offering many of the same services, and Walmart Neighborhood Market, a grocery-only store.
A little-known fact about Walmart is that the Supercenter concept spawned from a Flawed Prototype called Hypermart USA, which was deemed too inefficient, and collapsed after building only five locations.note
Sadly, due to widespread mismanagement at the retail store level, a lot of people (including both current and former employees) view it as the current Trope Codifier of Incompetence, Inc., having essentially succeeded WCW in said role.