  Let $E_G$ be a $\Gamma$--equivariant algebraic principal $G$--bundle over a
normal complex affine variety $X$ equipped with an action of $\Gamma$, where
$G$ and $\Gamma$ are complex linear algebraic groups. Suppose $X$ is
contractible as a topological $\Gamma$--space with a dense orbit, and $x_0 \in
X$ is a $\Gamma$--fixed point. We show that if $\Gamma$ is reductive, then
$E_G$ admits a $\Gamma$--equivariant isomorphism with the product principal
$G$--bundle $X \times_{\rho} E_G(x_0)$, where $\rho\,:\, \Gamma \,
\longrightarrow\, G$ is a homomorphism between algebraic groups. As a
consequence, any torus equivariant principal $G$-bundle over an affine toric
variety is equivariantly trivial. This leads to a classification of torus
equivariant principal $G$-bundles over any complex toric variety.
