在拓扑学中，单连通是拓扑空间的一种性质。直观地说，单连通空间中所有闭曲线都能连续地收缩至一点。此性质可以由空间的基本群刻划。

考虑道路连通之拓扑空间。若中的任意闭曲线皆同伦等价于一个点，则称该空间为单连通的。换言之，对任意连续映射

存在一点及同伦等价使得

另一种等价的叙述是：存在映射，其中表二维单位圆盘，使得。

若拓扑空间可写成单连通开子集之并，则称之为局部单连通。微分拓扑学所论的空间（例如流形）通常不外此类。

In topology, a topological space is called simply-connected (or 1-connected) if it is path-connected and every path between two points can be continuously transformed, staying within the space, into any other such path while preserving the two endpoints in question (see below for an informal discussion).