We evaluate the width of the $ω$ meson in nuclear matter. We consider the free decay mode of the $ω$ into three pions, which is dominated by $ρπ$ decay, and replace the $ρ$ and $π$ propagators by their medium modified ones. We also take into account the quasielastic and inelastic processes induced by a vector-baryon interaction dominated by vector meson exchange, as well as the contributions coming from the $ω\to K \bar K$ mechanism with medium modified $K$, $\bar K$ propagators. We obtain a substantial increase of the $ω$ width in the medium, reaching a value of $129 \pm 10$ MeV at normal nuclear matter density for an $ω$ at rest, which comes mainly from $ωN \to ππN, ωN N \to πNN$ processes associated to the dominant $ω\to ρπ$ decay mode. The value of the width increases moderately with momentum, reaching values of around 200 MeV at 600 MeV/c.

25 pages, 14 figures, revised version to appear published in Eur. Phys. J. A