We present a new measurement of the scaling relation between X-ray luminosity and total mass for 17,000 galaxy clusters in the maxBCG cluster sample . Stacking sub-samples within fixed ranges of optical richness , N _ { 200 } , we measure the mean 0.1-2.4 keV X-ray luminosity , \langle L _ { X } \rangle , from the ROSAT All-Sky Survey . The mean mass , \langle M _ { 200 } \rangle , is measured from weak gravitational lensing of SDSS background galaxies ( 12 ) . For 9 \leq N _ { 200 } < 200 , the data are well fit by a power-law , \langle L _ { X } \rangle / 10 ^ { 42 } h ^ { -2 } \mathrm { erg } \mathrm { s } ^ { -1 } = ( 12.6 ^ { +1. % 4 } _ { -1.3 } \mathrm { ( stat ) } \pm 1.6 \mathrm { ( sys ) } ) ( \langle M _ { 200 } \rangle / % 10 ^ { 14 } h ^ { -1 } M _ { \sun } ) ^ { 1.65 \pm 0.13 } . The slope agrees to within 10 \% with previous estimates based on X-ray selected catalogs , implying that the covariance in L _ { X } and N _ { 200 } at fixed halo mass is not large . The luminosity intercept is 30 \% , or 2 \sigma , lower than determined from the X-ray flux-limited sample of Reiprich & Böhringer ( 20 ) , assuming hydrostatic equilibrium . This slight difference could arise from a combination of Malmquist bias and/or systematic error in hydrostatic mass estimates , both of which are expected . The intercept agrees with that derived by Stanek et al . ( 25 ) using a model for the statistical correspondence between clusters and halos in a WMAP3 cosmology with power spectrum normalization \sigma _ { 8 } = 0.85 . Similar exercises applied to future data sets will allow constraints on the covariance among optical and hot gas properties of clusters at fixed mass .