Theory was founded in 1997 by Andrew Rosen (formerly of Anne Klein and Calvin Klein) and Elie Tahari. After successfully launching with their women's line, Theory added a line for men in 1999 followed by accessories a few years later. For 2011, Rosen recruited Olivier Theyskens to design a capsule collection, Theyskens' Theory, which resulted in Theyskens being appointed artistic director of the brand.