二分图又称双分图、二部图、偶图，指顶点可以分成两个不相交的集和（ ( and 皆为独立集independent sets)，使得在同一个集内的顶点不相邻（没有共同边）的图。

二分图又称作二部图，是图论中的一种特殊模型。 设G=(V,E)是一个无向图，如果顶点V可分割为两个互不相交的子集(U,V)，并且图中的每条边（i，j）所关联的两个顶点i和j分别属于这两个不同的顶点集(i in U,j in V)，则称图G为一个二分图。

无向图G为二分图的充分必要条件是，G至少有两个顶点，且其所有回路的长度均为偶数。

In the mathematical field of graph theory, a bipartite graph (or bigraph) is a graph whose vertices can be divided into two disjoint sets and (that is, and are each independent sets) such that every edge connects a vertex in to one in . Vertex sets and are usually called the parts of the graph. Equivalently, a bipartite graph is a graph that does not contain any odd-length cycles.