  We study the low-energy dynamics of noncommutative $\N=2$ supersymmetric U(N)
Yang-Mills theories in the Coulomb phase. Exact results are derived for the
leading terms in the derivative expansion of the Wilsonian effective action. We
find that in the infrared regime the U(1) subgroup decouples, and the remaining
SU(N) is described by the ordinary commutative Seiberg-Witten solution. IR/UV
mixing is present in the U(1), but not in SU(N). Our analysis is based on
explicit perturbative and multi-instanton calculations.
