Overstock.com, Inc. is an American internet retailer selling primarily furniture headquartered in Midvale, Utah, near Salt Lake City. Businessman Patrick M. Byrne founded Overstock.com in 1999. The company initially sold exclusively surplus and returned merchandise on an online e-commerce marketplace, liquidating the inventories of at least 18 failed dot-com companies at below-wholesale prices. The company continues to sell home decor, furniture, bedding, and many other goods that are closeout merchandise; however, it also sells new merchandise.

In May 2002, Overstock held an IPO at a per-share price of $13; furthermore, after achieving significant growth and profits in some early quarters, the company achieved a profit of $7.7 million in 2009 and reported its first billion-dollar year in 2010. The business started rebranding in early 2011, as "O.co", to simplify and unify its international operations but interrupted this effort a few months later, citing consumer confusion over the new name, which utilized a Colombian country domain.