We characterize mildly mixing group actions
of a noncompact, locally compact, second countable group $G$
using orbit equivalence. We show an amenable action $\Phi$
of
$G$ is mildly mixing if and only if $G$ is amenable and for
any nonsingular ergodic $G$-action $\Psi$, the product
$G$-action
$\Phi\times\Psi$ is orbit equivalent to $\Psi$. We extend
the result to the case of finite measure preserving
noninvertible endomorphisms, i.e., when $G=\N$, and show that
the theorem cannot be extended to include nonsingular
mildly mixing endomorphisms.