Stock symbol or Ticker symbol is a shorthand code used to uniquely identify shares of a publicly traded corporation in a particular stock exchange. A stock symbol may either be comprised of letters, numbers or a combination of both. The majority of symbols are comprised of letters. For example, MSFT is Microsoft, C is Citigroup, and GOOG is Google.

In the United States, modern letter-only ticker symbols were developed by Standard and Poor's (S&P) to bring a national standard to investing. Previously, a single company could have many different ticker symbols as they varied between the dozens of individual exchanges. The term ticker refers to the noise made by the ticker tape machines once widely used by stock exchanges. The S&P system was later standardized by the securities industry and modified as years passed.

For most stock symbols, the letters are simple identifiers. One or two-letter symbols always trade on the New York Stock Exchange (NYSE), three letter codes may trade on either the NYSE or American Stock Exchange (AMEX), and four and five-letter codes trade on the NASDAQ (although five-letter ticker symbols are usually a special class of stock). For example, the ticker symbols of mutual funds must be five letters long and end in "X".