Using (448.1 ± 2.9) × 106ψ(3686) events collected with the BESIII detector at the BEPCII collider, the decay ψ(3686) →Σ −Σ ¯ + is observed for the first time with a branching fraction of (2.82 ± 0.04stat.± 0.08syst.) × 10−4, and the angular parameter αΣ− is measured to be 0.96 ± 0.09stat.± 0.03syst.. [Figure not available: see fulltext.] © 2022, The Author(s).