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We report on the new Ruddlesden-Popper (RP) oxyfluoride La 2 NiO 2.5 F 3 containing an unprecedented high amount of fluorine and Ni 2+ . This oxyfluoride was prepared by topochemical low-temperature fluorination of La 2 NiO 4 , which was obtained by a soft chemistry synthesis, with poly(vinylidene difluoride) (PVDF) as fluorinating agent. La 2 NiO 2.5 F 3 is the first n = 1 RP compound crystallizing in the tetragonal space group P 4 2 / nnm ( a = 5.7297(6) Å and c = 13.0106(2) Å). The crystal structure shows a unique tilting scheme of the NiO 4 F 2 octahedra that has so far been only theoretically predicted. Combined neutron and X-ray powder diffraction experiments together with bond-valence-sum and DFT+U calculations reveal an unusual anion ordering with fluoride being located on the apical anion sites of the NiO 4 F 2 octahedra. Excess fluorine ions were found to populate two of the four interstitial anion sites in an ordered fashion. A third interstitial anion position is occupied by oxygen ions while the fourth site remains unoccupied. This hitherto unobserved ordering scenario in RP oxyfluorides promotes a strong layerwise alternating tilting of the NiO 4 F 2 octahedra. Magnetic measurements show strong antiferromagnetic interactions with a high Néel temperature of about 225 K and a pronounced ZFC/FC splitting most likely as the result of a small ferromagnetic moment arising from spin canting. The electronic structure was characterized by DFT and UV-vis spectroscopy, and a strong increase of E g was found compared to La 2 NiO 4 (3.4 eV vs 1.3 eV).