Abstract The proximity-coupling of a chiral non-collinear antiferromagnet (AFM) 1–5 with a singlet superconductor allows spin-unpolarized singlet Cooper pairs to be converted into spin-polarized triplet pairs 6–8 , thereby enabling non-dissipative, long-range spin correlations 9–14 . The mechanism of this conversion derives from fictitious magnetic fields that are created by a non-zero Berry phase 15 in AFMs with non-collinear atomic-scale spin arrangements 1–5 . Here we report long-ranged lateral Josephson supercurrents through an epitaxial thin film of the triangular chiral AFM Mn 3 Ge (refs. 3–5 ). The Josephson supercurrents in this chiral AFM decay by approximately one to two orders of magnitude slower than would be expected for singlet pair correlations 9–14 and their response to an external magnetic field reflects a clear spatial quantum interference. Given the long-range supercurrents present in both single- and mixed-phase Mn 3 Ge, but absent in a collinear AFM IrMn 16 , our results pave a way for the topological generation of spin-polarized triplet pairs 6–8 via Berry phase engineering 15 of the chiral AFMs.