A treasury stock or reacquired stock is stock which is bought back by the issuing company, reducing the amount of outstanding stock on the open market ("open market" including insiders' holdings).

Stock repurchases are often used as a tax-efficient method to put cash into shareholders' hands, rather than paying dividends. Sometimes, companies do this when they feel that their stock is undervalued on the open market. Other times, companies do this to provide a "bonus" to incentive compensation plans for employees. Rather than receive cash, recipients receive an asset that might appreciate in value faster than cash saved in a bank account. Another motive for stock repurchase is to protect the company against a takeover threat.

The United Kingdom equivalent of treasury stock as used in the United States is treasury share. Treasury stocks in the UK refers to government bonds or gilts.

When shares are repurchased, they may either be canceled or held for reissue. If not canceled, such shares are referred to as treasury shares. Technically, a repurchased share is a company's own share that has been bought back after having been issued and fully paid.