We report a comprehensive neutron diffraction study of the crystal structure and magnetic order in a series of single-crystal and powder samples of SrFeO_3-δ in the vacancy range 0 ≤ δ ≤ 0.23. The data provide detailed insights into the interplay between the oxygen vacancy order and the magnetic structure of this system. In particular, a crystallographic analysis of data on Sr₈Fe₈O₂₃ revealed a structural transition between the high-temperature tetragonal and a low-temperature monoclinic phase with a critical temperature T = 75 K, which originates from charge ordering on the Fe sublattice and is associated with a metal-insulator transition. Our experiments also revealed a total of seven different magnetic structures of SrFeO_3-δ in this range of δ, only two of which (namely an incommensurate helix state in SrFeO₃ and a commensurate, collinear antiferromagnetic state in Sr₄Fe₄O₁₁) had been identified previously. We present a detailed refinement of some of the magnetic ordering patterns and discuss the relationship between the magnetotransport properties of SrFeO_3-δ samples and their phase composition and magnetic microstructure.