We present TopMesh, a tool for extracting topological information from non-manifold three-dimensional objects with parts of non-uniform dimensions. The boundary of such objects is discretized as a mesh of triangles and of dangling edges, representing one-dimensional parts of the object. The geometrical and topological information extracted include the number of elements in the mesh, the number of non-manifold singularities and the Betti numbers, which characterize the topology of an object independently of the discretization of its boundary. TopMesh also computes a decomposition of the mesh into connected parts of uniform dimension, into edge-connected components formed by triangles, and into oriented edge-connected sub-meshes. We describe the functionalities of TopMesh and the algorithms implementing them.