We report experimental evidence for electron neutrino charged-current interactions (neutrino absorption, CC~${\nu }_e$) from ${}^8$B solar neutrinos on ${}^{40}$Ar using an exposure of (7.29 $\pm$ 0.05)~tonne$\cdot$years in the DEAP-3600 detector. A region of interest (ROI) of 10.5–13.0~MeV reconstructed energy calibrated on single-peak events, corresponding to incident neutrino energy in 12.0–14.5~MeV, is used for this measurement. We observe 5 single-peak and 1 double-peak neutrino-like events consistent with the ${}^8$B solar neutrino energy spectrum in the ROI after correcting for nonlinearities in the detector response at high energies. With an expected background of $0.48{}_{-0.15}^{+0.16}$ events, the background-only hypothesis is rejected at 4.0~$\sigma$. We report an energy-averaged cross section of $(4.0{}_{-1.6}^{+2.0}(stat){}_{-0.7}^{+0.8}(sys))\times {10}^{-41}{cm}^2$ in the ROI for the CC~${\nu }_e$ signal, a factor $(2.4{}_{-1.0}^{+1.3})$ higher than predicted by Bhattacharya, Goodman and Garc´ia (2009).