Ethalia guamensis, common name the Guam button top shell, is a species of sea snail, a marine gastropod mollusk in the family Trochidae, the top snails. The subspecies Ethalia guamensis montrouzieri (Souverbie, 1858) is a synonym of Rotella montrouzieri Souverbie, 1858, in turn a synonym of Ethalia montrouzieri.