Key reactions in which main-group systems have been studied are catalytic hydrodefluorination (HDF) and related defluorination processes (Scheme 1). These are important approaches to prepare complex fluorinated molecules, which have applications in pharmaceuticals, agrochemicals and materials chemistry, from readily available polyfluorinated precursors. Transition-metal-based C-F functionalisation is relatively well established, and a range of main-group systems have also been explored for HDF. These include non-redox systems such as strong Lewis acids and FLPs, which allow HDF of aliphatic C-F bonds, tetrabutylammonium triphenyldifluorosilicate (TBAT) , NaBH4 and diazaphospholenes, which can catalyse HDF of aromatic C-F bonds and trifluoromethylalkenes.