  We report the discovery of an arc-like object 27" from the center of the cD
galaxy in the redshift $z=0.066$ cluster A2124. Observations with the Keck II
telescope reveal that the object is a background galaxy at $z=0.573$,
apparently lensed into an arc of length \sim 8 \farcs5 and total R magnitude
$m_R = 20.86\pm0.07$. The width of the arc is resolved; we estimate it to be
$\sim$0\farcs6 after correcting for seeing. A lens model of the A2124 core mass
distribution consistent with the cluster galaxy velocity dispersion reproduces
the observed arc geometry and indicates a magnification factor $\gta $9. With
this magnification, the strength of the [OII] \lambda 3727 line implies a
star-formation rate of SFR \sim 0.4 h^{-2}\msun yr^{-1}$. A2124 thus appears to
be the lowest redshift cluster known to exhibit strong lensing of a distant
background galaxy.
