Flat or flats may refer to:

• Apartment, known as a flat in the United Kingdom, Ireland, and other Commonwealth countries

• Flat (music), a symbol (♭) which denotes a lower pitch
• Flat (soldier), a two-dimensional toy soldier made of tin or plastic
• Flat (theatre), a flat piece of theatrical scenery
• Flat, a leading type of wordplay, as identified by the National Puzzlers' League
• Flat! (2010), an Indian film
• Flats (band), an English band
• Flats (comics), the first stage in the comic coloring process

• Flats, footwear which is not high-heeled
• Ballet flats, derived from ballet shoes, for casual wear as well as dancing
• Ballet shoes (also known as ballet slippers), often referred to as "flats" or "flat shoes"
• Racing flats, lightweight shoes used primarily for running a race

• Flat (landform), a relatively level area within a region of greater relief

• Flat, a shallow water area in the context of boating, fishing or marine biology, often used in plural form
  • Brewster Flats, an area of Cape Cod Bay off the shore of Massachusetts, U.S.
  • Kentish Flats Offshore Wind Farm, off the coast of Kent, England
  • Rhyl Flats, a wind farm off the coast of North Wales
• Flat coast, a shoreline where the land descends gradually into the sea

• Flat, Alaska, a census-designated place
• Flat, Kentucky, an unincorporated community
• Flat, Missouri, an unincorporated community
• Flat, Texas, an unincorporated community
• Flat Brook, a tributary of the Delaware River in Sussex County, New Jersey
• Flats, Nebraska, United States
• Flats, West Virginia, an unincorporated community
• Forest Lake Area Trail System, Missouri

• Flat, Puy-de-Dôme, a commune in the French region of Auvergne
• Flat Island (disambiguation), in various places
• Flat Islands (disambiguation), in Canada and Antarctica
• Flat River (disambiguation), in the United States and Canada

• Flat (geometry), the generalization of lines and planes in an n-dimensional Euclidean space
• Flat (matroids), a further generalization of flats from linear algebra to the context of matroids
• Flat module in ring theory
• Flat morphism in algebraic geometry
• Flat space, a space with zero curvature
• Flat sign, for its use in mathematics; see musical isomorphism, mapping vectors to covectors

• Earl "Flat" Chase (1910–1954), Canadian baseball player
• Flat Walsh (1897–1959), Canadian ice hockey goaltender

• Flat Eric, a character in some Levi's commercials
• Flat Stanley, namesake of an American children's book series

• FLATS or First Lady Astronaut Trainees, American women who underwent NASA Project Mercury physiological screening tests

• Flat (gridiron football), the area of the gridiron football field
• Flat butterflies or flats, certain skipper butterfly genera in subfamily Pyrginae:
  • Calleagris (scarce flats),
  • Celaenorrhinus of tribe Celaenorrhinini;
  • Eagris, and
  • Tagiades (water flats, snow flats), of tribe Tagiadini
• Flats (USPS), an oversized letter
• Optical flat, an extremely flat piece of glass