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We report the discovery of the closest collisional ring galaxy to the MilkyWay. Such rare systems occur due to "bulls-eye" encounters between tworeasonably matched galaxies. The recessional velocity of about 840 km/s is lowenough that it was detected in the AAO/UKST Survey for Galactic H$\alpha$emission. The distance is only 10.0 Mpc and the main galaxy shows a full ringof star forming knots, 6.1 kpc in diameter surrounding a quiescent disk. Thesmaller assumed "bullet" galaxy also shows vigorous star formation. Thespectacular nature of the object had been overlooked because of its location inthe Galactic plane and proximity to a bright star and even though it is the60$^{\rm th}$ brightest galaxy in the HI Parkes All Sky Survey (HIPASS) HIsurvey.  The overall system has a physical size of $\sim$15 kpc, a total mass of$M_\ast = 6.6\times 10^9$ M$_\odot$ (stars + HI), a metallicity of[O/H]$\sim-0.4$, and a star formation rate of 0.2-0.5 M$_\odot$\,yr$^{-1}$,making it a Magellanic-type system. Collisional ring galaxies therefore extendto much lower galaxy masses than commonly assumed. We derive a space densityfor such systems of $7 \times 10^{-5}\,\rm Mpc^{-3}$, an order of magnitudehigher than previously estimated. This suggests Kathryn's Wheel is the nearestsuch system. We present discovery images, CTIO 4-m telescope narrow-bandfollow-up images and spectroscopy for selected emission components. Given itsproximity and modest extinction along the line of sight, this spectacularsystem provides an ideal target for future high spatial resolution studies ofsuch systems and for direct detection of its stellar populations.

Kathryns Wheel: A spectacular galaxy collision discovered in the Galactic neighbourhood