  We study bounded holomorphic functional calculus for nonsymmetric infinite
dimensional Ornstein-Uhlenbeck operators ${\mathscr L}$. We prove that if
$-{\mathscr L}$ generates an analytic semigroup on $L^{2}(\gamma_{\infty})$,
then ${\mathscr L}$ has bounded holomorphic functional calculus on
$L^{r}(\gamma_{\infty})$, $1<r<\infty$, in any sector of angle
$\theta>\theta^{*}_{r}$, where $\gamma_{\infty}$ is the associated invariant
measure and $\theta^{*}_{r}$ the sectoriality angle of ${\mathscr L}$ on
$L^{r}(\gamma_{\infty})$. The angle $\theta^{*}_{r}$ is optimal. In particular
our result applies to any nondegenerate finite dimensional Ornstein-Uhlenbeck
operator, with dimension-free estimates.
