A backbone network is the top level of a hierarchical computer network. It connects to nodes at lower levels in the hierarchy.

Backbone networks often exist solely to provide connectivity between lower-level networks. In the early days of the Internet, a single backbone network existed in the form of first the ARPANET and later the NSFNET. All other networks connected with one another via the Internet backbone, and routing information was conveyed between the backbone and the other networks via the Exterior Gateway Protocol (EGP).

Today, there is no single backbone network for the Internet. Rather, each Internet service provider has its own backbone network, and exchanges traffic with other networks by peering, or by transit agreements.