In computing, a Control key is a modifier key which, when pressed in conjunction with another key, will perform a special operation (for example, Control-Alt-Delete); similar to the Shift key, the Control key rarely performs any function when pressed by itself. The control key is located on or near the bottom left side of most keyboards, with many featuring an additional one at the bottom right. It is usually labeled Ctrl, but sometimes Control or Ctl is seen, and it can be graphically represented as an “up arrowhead” (U+2303, ⌃), or simulated with a caret (^).

On teletypewriters and early keyboards, holding down the Control key while pressing another key zeroed the leftmost 2 bits of the 7 bits in the generated ASCII character. This allowed the operator to produce the first 32 characters in the ASCII table. These are non-printing characters that signal the computer to control where the next character will be placed on the display device, eject a printed page or erase the screen, ring the terminal bell, or some other operation. Aptly, these characters are also called control characters. In German keyboards, it is called a Strg key.