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We present a Rayleigh wave tomographic study of the upper mantle beneath the Galápagos Archipelago. We analyze waves in 12 separate frequency bands (8–50 mHz) sensitive to shear wave velocity (V_S) structure in the upper 150 km. Average phase velocities are up to 2 and 8% lower than for 0‐ to 4‐My‐old and 4‐ to 20‐My‐old Pacific seafloor, respectively. Laterally averaged V_S is 0.05–0.2 km/s lower between 75‐ and 150‐km depth than for normal Pacific mantle of comparable age, corresponding to an excess temperature of 30 to 150°C and ∼0.5% melt. A continuous low‐velocity volume that tilts in a northerly direction as it shoals extends from the bottom of our model to the base of a high‐velocity lid, which is located at depths varying from 40 to 70 km. We interpret this low‐velocity volume as an upwelling thermal plume that flattens against the base of the high‐velocity lid. The high‐velocity lid is ∼30 km …