  We interpret the recent gravitational lensing observations of Jee et al.
\cite{Jee} as first evidence for a {\it caustic} ring of dark matter in a
galaxy cluster. A caustic ring unavoidably forms when a cold collisionless flow
falls with net overall rotation in and out of a gravitational potential well.
Evidence for caustic rings of dark matter was previously found in the Milky Way
and other isolated spiral galaxies. We argue that galaxy clusters have at least
one and possibly two or three caustic rings. We calculate the column density
profile of a caustic ring in a cluster and show that it is consistent with the
observations of Jee et al.
