Dolphin shorts are an athletic style of shorts. They are notable for a visible binding of an often contrasting color, often white. The main body of the shorts are often one bright block color, but there is much color variation.
The name may refer to the Dolfin swimwear company, which helped to popularize the style, or to a side-on viewing of the binding of each leg's lower hem, resembling the shape of a dolphin tail. Like gym shorts, they often feature a cord to be tied around the waist at the front. Dolfin extended their product line into running wear from their mainstay product, nylon swimsuits for competitive swimmers.
These were a popular trend in the 1980s fashion, and have been brought back many years later, especially in 2006/2007, particularly in the fitness and gym scene. They are also popularized by Richard Simmons.