Herein, we report a powerful method for the cyclisation of peptides via desulfurative C(sp 3 )-C(sp 3 ) bond formation. Our approach is operationally simple, effective 'on the bench' under ambient conditions with irradiation of blue light, utilising readily available starting building blocks. The reaction is rapid, high yielding (for most cases studied) on unprotected peptides in aqueous solution and tolerant to all proteinogenic chemical functionality. The technique enables the preparation of a range of macrocycle sizes and extends to internal macrocyclisation (peptide stapling). This technology presents a more sustainable alternative to the widely employed RCM, offering an effective new method of peptide cyclisation.