A sweatshirt is a long-sleeved pullover shirt or jacket fashioned out of thick, usually cotton, cloth material.^[1][2] Sweatshirts are almost exclusively casual attire and hence not as formal as some sweaters. Sweatshirts may or may not have a hood. A sweatshirt with a hood is now usually referred to as a hoodie, although more formal media still use the term "hooded sweatshirt".

In 1920, Benjamin Russell Jr., a quarterback for the Alabama Crimson Tide Football team, was tired of the constant chafing and itching caused by their wool football uniforms.^[3] He worked with his father, whose company Russell Manufacturing Company made women's and children's knit garments, to come up with a better option.^[4] They created a thick cotton practice jersey that was a modification of a ladies' union suit top.^[5] These loose, collarless pullovers were the first sweatshirts. A new division of the company, focusing solely on the production of sweatshirts, became the Russell Athletic Company.

The sweatshirt's potential as a portable advertising tool was discovered in the 1960s when U.S. universities began printing their names on them to exhibit school pride. The sweatshirt, along with the T-shirt, provided a cheap and effective way of disseminating information on a mass scale. The T-shirt slogan fad of the 1970s inevitably translated to sweatshirts. Due to the relative simplicity of customization and the power of clever graphics combined with catchphrases, sweatshirts became a vehicle for personal expression for both the designer and the wearer.^[6]

In Australia, the sweatshirt is referred to as a 'Sloppy Joe'. ^{[citation needed]}