The BNC connector is a type of RF connector used for terminating coaxial cable. The connector was named after its bayonet mount locking mechanism and its two inventors, Paul Neill of Bell Labs (inventor of the N connector) and Amphenol engineer Carl Concelman (inventor of the C connector). It is a lot smaller than N and C connectors. Nicknames the BNC has picked up over the years include: "Baby Neill-Concelman", "Baby N connector", "British Naval Connector", "Bayonet Nut Connector".

The BNC connector is used for professional video connections, both for analog and Serial Digital Interface signals, amateur radio antenna connections, and on nearly every piece of electronic test equipment manufactured in the last 35 or so years. This connector is an alternative to the RCA connector when used for composite video on commercial video devices, however many consumer electronics with RCA jacks have been utilized on commercial video equipment with BNC jacks via adaptor. BNC connectors were commonly used on 10base2 thin Ethernet networks, both on cable interconnections and network cards, though these have largely been replaced by newer Ethernet devices whose wiring does not use coaxial cable. Some ARCNET networks use BNC terminated coax.

A threaded version of the BNC connector, known as the TNC connector (for Threaded Neill-Concelman) is also available. It has superior performance to the BNC connector at microwave frequencies.

The BNC connectors are commonly used in NIM electronics, but they are now often replaced by LEMO miniature connectors which allow for higher densities.