We report the first single-molecule magnet (SMM) to incorporate the [Os(CN)₆]^3- moiety. The compound (1) has a trimeric, cyanide-bridged Mn^III-Os^III-Mn^III skeleton in which Mn^III designates a [Mn(5-Brsalen)(MeOH)]⁺ unit (5-Brsalen=N,N′-ethylenebis(5-bromosalicylideneiminato)). X-ray crystallographic experiments reveal that 1 is isostructural with the Mn ^III-Fe^III-Mn^III analogue (2). Both compounds exhibit a frequency-dependent out-of-phase π″(T) alternating current (ac) susceptibility signal that is suggestive of SMM behaviour. From the Arrhenius expression, the effective barrier for 1 is found to be Δ_eff/k_B=19a K (τ₀=5.0× 10 ^-7a s; k_B=Boltzmann constant), whereas only the onset (1.5a kHz, 1.8a K) of π″(T) is observed for 2, thus indicating a higher blocking temperature for 1. The strong spin-orbit coupling present in Os ^III isolates the E′_1g(1/2)(O_h*) Kramers doublet that exhibits orbital contributions to the single-ion anisotropy. Magnetic susceptibility and inelastic neutron-scattering measurements reveal that substitution of [Fe(CN)₆]^3- by the [Os(CN)₆]^3- anion results in larger ferromagnetic, anisotropic exchange interactions going from quasi-Ising exchange interactions in 2 to pure Ising exchange for 1 with J_∥^MnOs = -30.6a cm^-1. The combination of diffuse magnetic orbitals and the Ising-type exchange interaction effectively contributes to a higher blocking temperature. This result is in accordance with theoretical predictions and paves the way for the design of a new generation of SMMs with enhanced SMM properties. The iron age to the osmium age: Introduction of [Os(CN) ₆]^3- in single-molecule magnets instead of [Fe(CN) ₆]^3- leads to an increase in the blocking temperature due to stronger exchange interactions and orbital contributions that arise from the unquenched orbital angular momentum of the octahedral Os^III ion (see figure).