The crystal structure and luminescence properties of flux-grown crystals of a new europium(III) fluoride-silicate, K5Eu2FSi 4O13, are reported. The structure consists of octahedral dimers of the composition [Eu2O10F], which are linked by unbranched tetrasilicate chains to form a 3-D framework with 5- and 6-ring channels parallel to the b axis where the K+ cations are located. The sharp peaks in the room-temperature emission spectrum are assigned. The number of lines in the region for the 5D0 → 7F0 transition and the relative intensities of the 5D0 → 7F1 and 5D0 → 7F2 transitions confirm the presence of two local Eu3+ environments and strongly distorted Eu3+-ligand surroundings. The room-temperature fluorescence decay curves are well fit by a single-exponential function yielding a lifetime value of about 2.0 ms. Crystal data: monoclinic, space group P21/m, a = 7.1850(2) Å, b = 5.7981(2) Å, c = 18.1675(6) Å, β = 92.248(2)°, and Z = 2.