Two salts containing diphosphorus-centered radical anion 1(•-) and diradical dianion 1(2-••) were obtained by one- and two-electron reductions of an indenofluorene-bridging diphosphaalkene (1) with K and KC8, respectively. The salts have been characterized by electron paramagnetic resonance (EPR) spectroscopy, UV-vis absorption spectroscopy, and single-crystal X-ray diffraction analysis. EPR spectroscopy and theoretical calculations reveal that the spin density of the radicals mainly resides on the phosphorus atoms, and 1(2-••) has an open-shell singlet ground state. 1(•-) and 1(2-••) represent the first isolable and structurally characterized diphosphorus-centered radical anion and dianion.