Rare-earth metal ions (Sc, Y, lanthanides) have attracted significant attention, mainly due to their Lewis acidity and oxophilicity. In particular, Sc(OTf)3 has been introduced in recent decades as a promising Lewis acid for C-H functionalisation and C-C bond formation reactions. In the past 20 years, scandium salts have also effectively assumed a role in photoredox catalysis-a process that has emerged as a full-fledged alternative in organic synthesis, often unlocking transformations that are not attainable in the dark. Photoredox catalysis relies on an electron transfer process between a highly reactive, light-excited catalyst and a redox-labile substrate (S). The result is a reactive radical intermediate that undergoes further transformations, ultimately resulting in the formation of new bonds under mild conditions. Photoredox catalysis requires a catalyst that is both photochemically and redox active-typically a compound derived from an organic dye or a complex of a redox-active metal, such as ruthenium or iridium (see Fig. ). Conversely, redoxinactive/innocent metals, such as scandium, which have a predominantly trivalent redox-stable state, are not directly involved in photoredox reactions. Nevertheless, these metals, and particularly Sc(OTf)3, can serve as Lewis acids (LA) that activate substrates/organophotocatalysts by altering their redox characteristics, thereby facilitating their participation in photoredox and photosensitisation reactions (Figs. and). For instance, the redox properties of a flavin derivative (Fl) were significantly enhanced via their coordination to Sc(OTf)3. This alteration enabled the oxidation of some electron-deficient substrates via a SET process between the substrate and flavin in excited Fl-2Sc 3+ complex (Fig. , right); such reaction cannot be achieved without Sc(OTf)3. Notably, the oxophilicity of some M n+ cations facilitates their binding to superoxide radical anion (O2 •-) to form superoxide-metal complexes (M n+ -O2 •-) that have been recognised within the reductive activation of dioxygen by metalloenzymes in numerous biological redox reactions that employ O2 as an oxidant. This process has been mimicked in the dioxygen activation cycle during photoredox transformations, commencing with the photoinduced single electron transfer (PET) from a light-absorbing, redox-active compound to O2 and followed by the generation of M n+ -O2 •-complexes (Fig. , upper part). Binding of M n+ to oxygen enhances its ability to accept an electron. Thus, an electron transfer from donor (D) to O2, which is thermodynamically infeasible in the absence of metal ions, becomes possible in the presence of M n+ . This process is generally called metal ion-coupled electron transfer (MCET). Scandium 3+ ion, with its smallest radius among M 3+ , can bind strongly with O2 •-, making it far more effective than other M n+ ions for providing SET reactions driven by M n+ -O2 •-complex formation A review of previous reports on the role of Sc(OTf)3 in photoinduced electron transfer (PET) transformations involving the reductive activation of dioxygen confirms that a light-absorbing electron donor and additional stabilisation are necessary. For example, Fukuzumi recorded the EPR spectrum of the (HMPA)3Sc 3+ -O2 •-complex stabilised by three equivalents of hexamethylphosphoramide (HMPA) ligand, formed via PET from the singlet excited state of 1-benzyl-1,4-dihydronicotinamide dimer 1 [(BNA)2]*, to O2. This procedure was accompanied by fast cleavage of the C-C bond in the formed (BNA)2 •+ (Fig. , bottom part). Our present study is the first report to demonstrate the activity of Sc(OTf)3 functioning as a sole photoredox catalyst. Sc(OTf)3 is shown to facilitate aerobic oxidation of a benzylic C-H bond and direct oxidative cyanation of arenes as examples of C-H activation and C-C coupling reactions (Fig. ). These unprecedented procedures dispel the usual notion of scandium salts as redox-inactive species useful mostly as Lewis acids and expand their possible application as simple, readily available photocatalysts. In general, photoredox processes might be a further application of scandium, which is abundantly found on earth but remains an underutilised metal. 30