Monoxia obesula Blake, 1939, a species native to North America, is newly found in Sardinia, Italy. This discovery constitutes the first report of the species from Europe, as well as the first report from outside of the U.S.A. The species is redescribed and illustrated, and errors in the original description are corrected. Host plants are species of Atriplex and Chenopodium occurring in saline habitats.