A stock transfer agent, transfer agent, share registry or transfer agency is an entity, usually a third party firm unrelated to security transactions, that manages the change in ownership of company stock or investment fund shares, maintains a register of ownership and acts as paying agent for the payment of dividends and other distributions to investors. The name derives from the impartial intermediary role a transfer agent plays in validating and registering the purchase of new ownership shares and, in the case of a transfer of ownership, cancelling the name and certificate of shareholders who sell shares and substituting the new owner's name on the official master shareholder register.

Transfer agent or stock transfer agent is the term used in the United States and Canada. Share registry is used in the United Kingdom, Australia and New Zealand. Transfer secretary is used in South Africa. A company may act as its own transfer agent or engage a third-party company to perform shareholder registry services. Transfer agents in the United States must be registered with the Securities and Exchange Commission (SEC) or a bank regulatory agency.

For investment funds, transfer agent functions and fund administration are interdependent, making it desirable in some cases for fund managers to assign both services to a single third party. Transfer agent service providers may offer their services along with fund accounting, fund administration and other outsourced back-office services as a "package" for the convenience of client companies.