In electronics, a pinout (sometimes written "pin-out") is a cross-reference between the contacts, or pins, of an electrical connector or electronic component, and their functions.

The functions of contacts in electrical connectors, be they power- or signaling-related, must be specified in order for connectors to be interchangeable. When connected, each contact of a connector must mate with the contact on the other connector that has the same function. If contacts of disparate functions are allowed to make contact, the connection may fail and damage may result. Therefore, pinouts are a vital reference when building and testing connectors, cables, and adapters .

While one usage of the word pin is to refer to electrical contacts of, specifically, the male gender, its usage in pinout does not imply gender: the contact-to-function cross-reference for a connector that has only female socket contacts is still called a pinout.

The pinout can typically be shown as a table or diagram, though it is necessary to clarify how to view the diagram, stating if it shows the backside of the connector (where wires are attached) or the "mating face" of the connector. Published pinouts, which are particularly important when different manufacturers want to interconnect their products using open standards, are typically provided by the connector or equipment manufacturer. Some pinouts are provided by 3rd parties since some connectors are not well documented by the manufacturer.