Internetworking is the practice of interconnecting multiple computer networks,^: 169 such that any pair of hosts in the connected networks can exchange messages irrespective of their hardware-level networking technology. The resulting system of interconnected networks are called an internetwork, or simply an internet.

The most notable example of internetworking is the Internet, a network of networks based on many underlying hardware technologies. The Internet is defined by a unified global addressing system, packet format, and routing methods provided by the Internet Protocol.^: 103

The term internetworking is a combination of the components inter (between) and networking. An earlier term for an internetwork is catenet, a short-form of (con)catenating networks.