Linked from
The 31 pages that link to Complete graph, each with the reason it gives.
Simple graphBroader topic: It is the maximally connected simple graph on a fixed number of vertices.
Line graphBroader topic: The line graph of a complete graph displays dense edge-incidence structure.
Connected graphBroader topic: Every complete graph is connected, with each pair linked directly.
TreewidthBroader topic: A complete graph on n vertices has treewidth n minus one.
Vertex-transitive graphBroader topic: Every permutation of its vertices is an automorphism.