We present the first weak gravitational lensing analysis of the completed Canada-France-Hawaii Telescope Legacy Survey ( CFHTLS ) . We study the 64 ~ { } { deg } ^ { 2 } W1 field , the largest of the CFHTLS-Wide survey fields , and present the largest contiguous weak lensing convergence “ mass map ” yet made . 2.66 million galaxy shapes are measured , using a Kaiser , Squires and Broadhurst ( KSB ) pipeline verified against high-resolution Hubble Space Telescope imaging that covers part of the CFHTLS . Our i ^ { \prime } -band measurements are also consistent with an analysis of independent r ^ { \prime } -band imaging . The reconstructed lensing convergence map contains 301 peaks with signal-to-noise ratio \nu > 3.5 , consistent with predictions of a \Lambda CDM model . Of these peaks , 126 lie within 3 \arcmin . 0 of a brightest central galaxy identified from multicolor optical imaging in an independent , red sequence survey . We also identify seven counterparts for massive clusters previously seen in X-ray emission within 6 ~ { } deg ^ { 2 } XMM-LSS survey . With photometric redshift estimates for the source galaxies , we use a tomographic lensing method to fit the redshift and mass of each convergence peak . Matching these to the optical observations , we confirm 85 groups/clusters with \chi ^ { 2 } _ { \mathrm { reduced } } < 3.0 , at a mean redshift \langle z _ { c } \rangle = 0.36 and velocity dispersion \langle \sigma _ { c } \rangle = 658.8 ~ { } km~ { } s ^ { -1 } . Future surveys , such as DES , LSST , KDUST and EUCLID , will be able to apply these techniques to map clusters in much larger volumes and thus tightly constrain cosmological models .