A period key is a key found on a computer keyboard that produces a period (.) symbol when pressed. It is also known as a full stop or dot. On U.S. keyboards, the period key is located next to the question mark key. On keyboards with numeric keypads, the period key is also located next to the Enter key. To create a period on a U.S. keyboard, simply press the period key with no other key. On a smartphone or tablet, the period symbol can be found in the numbers (123) or symbols (sym) section of the keyboard.

The period symbol is used in various ways on a computer, such as in file names and extensions, as a wildcard in programming code, and to represent the current directory in Linux.

It is worth noting that the term "period key" can also refer to a set of cryptographic key details that are kept unchanged during an agreed time. However, this is not related to the computer keyboard key that produces a period symbol.