The Mediterranean species Lythrum junceum Banks & Sol. is newly reported from California, based on multiple records from southwestern Alameda County and adjacent Santa Clara County. Previous collections, dating to at least 1905, were misidentified as L. californicum Torr. & A.Gray, but differ in their sprawling habit, white-based petals, and purple-spotted hypanthia. Diagnostic features, invasive potential, and speculations on origin are addressed. In addition, two species of Lythrum described from California in 1889 are typified: a lectotype for L. adsurgens Greene and a neotype for L. sanfordii Greene. The possible role of hybridization in the establishment of L. hyssopifolia L. and other introduced species of Lythrum in California is also discussed.