The late Quaternary plinian eruption forming the Kos Plateau Tuff on the island of Kos, Greece, was one of the largest in the Mediterranean. A precise date for this eruption would significantly improve the chronology of the deep‐sea tephra layer W‐3, because reliable correlation of W‐3 with the KOS Plateau Tuff has been previously established. We have dated sanidine from the eruption at 161.3±1.1 ka using the laser‐fusion single crystal ⁴⁰Ar‐³⁹Ar technique. This age represents a significant refinement over both conventional and highly precise (Cassignol method) K‐Ar ages, and the ⁴⁰Ar‐³⁹Ar age is shown to be in remarkably good agreement with the age of W‐3 inferred from recent astronomically calibrated oxygen isotope chronologies.