  To every group $G$ we associate a linear monoidal category
$\mathcal{P}\mathit{ar}(G)$ that we call a group partition category. We give
explicit bases for the morphism spaces and also an efficient presentation of
the category in terms of generators and relations. We then define an embedding
of $\mathcal{P}\mathit{ar}(G)$ into the group Heisenberg category associated to
$G$. This embedding intertwines the natural actions of both categories on
modules for wreath products of $G$. Finally, we prove that the additive Karoubi
envelope of $\mathcal{P}\mathit{ar}(G)$ is equivalent to a wreath product
interpolating category introduced by Knop, thereby giving a simple concrete
description of that category.
