In conclusion, we have identified a new strategy for the single-electron oxidative activation of bicyclo[1.1.0]butane via photoredox catalysis. The synthetic utility of the resulting radical cation was highlighted by its ability to undergo [2π+2σ] cycloaddition reactions in a highly regio-and diastereoselective fashion. The scope of the transformation with respect to the alkene coupling partner was remarkably broad, allowing the cycloaddition of styrene-type, heteroatom substituted and, for the first time in this reaction class, non-activated alkenes. A comprehensive experimental and computational mechanistic study was undertaken that confirmed the involvement of BCB radical cations and illuminated the nature of their interaction with olefins. We foresee that the work presented above can serve as a platform from which further studies into the potential synthetic applications of bicyclo[1.1.0]butyl radical cations can be built upon.