A Palearctic spider, Linyphia triangularis (Clerck 1757), has been accidentally introduced to the U.S.A. and populations successfully established in Maine. The date, origin, and focal point(s) of introduction are unknown, but suspected to be recent, European, and maritime. Extensive historical collections, records of maritime commerce, and recent chronological collections support this hypothesis. Results of cursory surveys in 1999 and 2000 indicate that L. triangularis is now widely distributed in Maine with specimens taken in 15 of 16 counties. The potential impact(s) of L. triangularis on the native araneofauna are unknown, but possibly detrimental. In Europe, this species exhibits aggressive behaviors (e.g., web “take-overs”) toward conspecifics and congenerics.