This report describes the development of a visible-light photocatalytic system for C(sp2)-H amination that leverages in situ-generated photocatalysts. We demonstrate that the combination of acridine derivatives and Lewis acids forms potent photooxidants that promote the C-H amination of electronically diverse arenes upon irradiation with visible-light (440 nm). A first-generation photocatalyst composed of Sc(OTf)3 and acridine effects the C-H amination of substrates with oxidation potentials ≤ +2.5 V vs SCE with pyrazole, triazole, and pyridine nucleophiles. Furthermore, the simplicity and modularity of this system enable variation of both Lewis acid and acridine to tune reactivity. This enabled the rapid identification of two second-generation photocatalysts (derived from (i) Al(OTf)3 and acridine or (ii) Sc(OTf)3 and a pyridinium-substituted acridine) that catalyze a particularly challenging transformation: C(sp2)-H amination with benzene as the limiting reagent.