Flatiron or flat iron may refer to various things, often in the shape of a wedge:

• Clothes iron
• Hair iron

• Flatiron Building, New York City, at the intersection of 5th & Broadway
  • Flatiron District, New York City, named after the Flatiron Building
• List of Flatiron buildings, including many similar buildings
• Flat Iron, Indiana, a small community in Vermillion County
• Flat Iron, Virginia
• Flatirons Community Church, a large non-denominational church in Lafayette, Colorado

• Flatiron (geomorphology), a steeply sloping wedge shaped landscape feature
  • Flatirons, rock formations near Boulder, Colorado
  • Flatiron (volcano), a volcano in Wells Gray Park, British Columbia, Canada
  • The Flatiron, a headland overlooking Granite Harbour, Victoria Land, Antarctica

• The Flatiron (photograph), a 1904 photograph by Edward Steichen
• Flatiron Books, a division of Macmillan Publishers
• Flat Iron, a First Nations lacrosse player who competed in the 1904 Summer Olympics for Canada
• Flat-iron gunboat, a 19th-century iron gunboat typified by a single large gun fitted in the bow
• Flatiron (ship), a type of British ship for passing under low bridges
• Flat iron steak, a cut of beef
• Flatiron Construction, a civil infrastructure construction firm