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We present optical and near-infrared UBVRIJHK photometry of stars in theGalactic globular cluster M4 (NGC 6121) based upon a large corpus ofobservations obtained mainly from public astronomical archives. We concentrateon the RR Lyrae variable stars in the cluster, and make a particular effort toaccurately reidentify the previously discovered variables. We have alsodiscovered two new probable RR Lyrae variables in the M4 field: one of them byits position on the sky and its photometric properties is a probable member ofthe cluster, and the second is a probable background (bulge?) object. Weprovide accurate equatorial coordinates for all 47 stars identified as RRLyraes, new photometric measurements for 46 of them, and new period estimatesfor 45. We have also derived accurate positions and mean photometry for 34 morestars previously identified as variable stars of other types, and for anadditional five non-RR Lyrae variable stars identified for the first time here.We present optical and near-infrared color-magnitude diagrams for the clusterand show the locations of the variable stars in them. We present the Bailey(period-amplitude) diagrams and the period-frequency histogram for the RR Lyraestars in M4 and compare them to the corresponding diagrams for M5 (NGC 5904).We conclude that the RR Lyrae populations in the two clusters are quite similarin all the relevant properties that we have considered. The mean periods,pulsation-mode ratios, and Bailey diagrams of these two clusters show supportfor the recently proposed "Oosterhoff-neutral" classification.

Optical and Near-Infrared UBVRIJHK Photometry for the RR Lyrae stars in the Nearby Globular Cluster M4 (NGC 6121)