- - - Department of Pure Mathematics, Ferdowsi University of Mashhad, Mashhad, Iran.
- - - Department of Pure Mathematics, Ferdowsi University of Mashhad, Mashhad, Iran.

In this article, we introduce the concept of co-covering which is the dual of covering concept. Then, we prove several theorems being similar to the theorems that have been de-veloped for the covering concept. For example, we provide the lifting criterion for co-coverings of a topological space X, which helps us to classify them by subgroups of the group of all homeomorphisms of X.

Covering map, Covering space, Co-covering