Common stock is a form of corporate equity ownership, a type of security. The terms "voting share" or "ordinary share" are also used in other parts of the world; common stock being primarily used in the United States.

It is called "common" to distinguish it from preferred stock. If both types of stock exist, common stock holders cannot be paid dividends until all preferred stock dividends (including payments in arrears) are paid in full.

In the event of bankruptcy, common stock investors receive any remaining funds after bondholders, creditors (including employees), and preferred stock holders are paid. As such, such investors often receive nothing after a bankruptcy.

On the other hand, common shares on average perform better than preferred shares or bonds over time.

Common stock usually carries with it the right to vote on certain matters, such as electing the board of directors. However, a company can have both a "voting" and "non-voting" class of common stock.

Holders of common stock are able to influence the corporation through votes on establishing corporate objectives and policy, stock splits, and electing the company's board of directors. Some holders of common stock also receive preemptive rights, which enable them to retain their proportional ownership in a company should it issue another stock offering. There is no fixed dividend paid out to common stock holders and so their returns are uncertain, contingent on earnings, company reinvestment, efficiency of the market to value and sell stock.