"Frichs Firkant" (which translates to "The Frichs Square") is a famous and iconic series of Danish diesel-electric locomotives produced by the manufacturing company A/S Frichs in Aarhus, Denmark, starting in 1932.

These locomotives earned the nickname "Firkant" (The Square) because their design was extremely boxy and built purely for practicality. In an era where people were used to the large, rounded boilers of steam locomotives, the square steel body was a striking departure in aesthetics. The shape was chosen to maximize space for the large diesel engine and to make maintenance as easy as possible.

Their appearance also earned them other affectionate (and less affectionate) nicknames among railway workers, including "Kiksekasser" (Biscuit Boxes) and "Standkister" (Upright Chests).