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