We report the discovery of a binary galaxy cluster merger via a search of the redMaPPer optical cluster catalog, with a projected separation of 535kpc between the brightest cluster galaxies (BCGs). Archival XMM-Newton spectro-imaging reveals a gas peak between the BCGs, suggesting a recent pericenter passage. We conduct a galaxy redshift survey to quantify the line-of-sight velocity difference (153+/-281km/s) between the two subclusters. We present weak-lensing mass maps from archival Hubble Space Telescope Advanced Camera for Surveys (HST/ACS) imaging, revealing masses of M_200_=4.5+/-0.8x10^14^ and 2.8+/-0.7x10^14^M_{sun} associated with the southern and northern galaxy subclusters, respectively. We also present deep GMRT 650MHz data revealing extended emission, 420kpc long, which may be an active galactic nucleus (AGN) tail but is potentially also a candidate radio relic. We draw from cosmological n-body simulations to find analog systems, which imply that this system is observed fairly soon (60-271Myr) after pericenter, and that the subcluster separation vector is within 22{deg} of the plane of the sky, making it suitable for an estimate of the dark matter scattering cross section. We find {sigma}_DM/m=1.1+/-0.6cm^2^/g, suggesting that further study of this system could support interestingly tight constraints.

Cone search capability for table J/ApJ/954/36/table1 (Galaxy redshifts)