A complete graph is a simple graph where an edge connects every pair of vertices. A complete graph on n vertices has n vertices and n(n−1)/2 edges, and is indicated by the notation Kn. It is a regular graph of valence n−1.

A complete bipartite graph is a graph with vertices segregated into two sets, where an edge connects every pair of vertices where they are not in the same set.

Complete graphs on n vertices, for n between 1 and 8, are shown below:

       

   
   
   
   
nKn nKn
1 5
2 6
3 7
4                    8