A foam is a substance that is formed by trapping pockets of gas in a liquid or solid. A bath sponge and the head on a glass of beer are examples of foams. In most foams, the volume of gas is large, with thin films of liquid or solid separating the regions of gas.

Foam may refer to:

• Foam, a substance that is formed by trapping gas bubbles in a liquid or solid.
• Foam (culinary), a modern food preparation and presentation technique
• Foam (organization), known as FoAM, an art and technology organization
• Foam hand, a sports paraphernalia item
• Foam Fotografiemuseum Amsterdam, known as FOAM, a photography museum in Amsterdam
• OpenFOAM, an open source finite volume pde solver used in a variety of computational fluid dynamics applications
• , a United States Navy trawler and minesweeper in commission from 1918 to 1919
• First Office Action on the Merits, a form of Office action in United States patent law
• Flag officer#United Kingdom Attached Middle East, a former major command of the Royal Navy