  When an asymptotically non-free theory possesses a mass parameter, the
ultraviolet (UV) renormalon gives rise to non-perturbative contributions to
dimension-four operators and dimensionless couplings, thus has a similar effect
as the instanton. We illustrate this phenomenon in O(N) symmetric massive
$\lambda\phi^4$ model in the $1/N$ expansion. This effect of UV renormalon is
briefly compared with non-perturbative corrections in the magnetic picture of
the Seiberg-Witten theory.
