Two‐electron reduction of carbene‐supported 9‐bromo‐9‐borafluorenes with excess KC₈, Na, or Li‐naphthalenide affords six N‐heterocyclic carbene (NHC)‐ or cyclic(alkyl)(amino) carbene (CAAC)‐stabilized borafluorene anions ( 3‐8 )−the first isolated and structurally authenticated examples of the elusive 9‐carbene‐9‐borafluorene monoanion. The electronic structure, bonding, and aromaticity of the boracyclic anions were comprehensively investigated via computational studies. Compounds  5  and  8  react with metal halides via salt elimination to give new B−E (E = Au, Se, Ge)‐containing materials ( 9 ‐ 12 ). Upon reaction with diketones, the carbene ligand cleanly dissociates from  5  or  8  to yield new B−O containing spirocycles ( 13 ‐ 14 ) that cannot be easily obtained using "normal" valent borafluorene compounds. Collectively, these results support the notion that carbene‐stabilized monoanionic borafluorenes may serve as a new platform for the one‐step construction of higher‐value boracyclic materials.