All known Belgian herbarium specimens of the genus Amsinckia, housed in the three largest public herbaria (BR, LG, and GENT) and in selected private collections, were critically revised. Six species were identified: A. eastwoodiae, A. intermedia, A. lycopsoides, A. micrantha, A. retrorsa, and A. tessellata. Of these, A. eastwoodiae, A. retrorsa and A. tessellata are only known from historical collections, with no records after 1953. A. intermedia and A. lycopsoides, though mostly recorded in the past, have recently been rediscovered. The most recent introduction is A. micrantha, first observed in 1979, which has since become clearly naturalised, particularly on sandy soils in the northern part of the country. Its earliest stable populations date to the late 1980s.
Taxonomic and nomenclatural issues are addressed, including the distinction between A. micrantha and its South American relative A. calycina, and the invalidity of the widely used name A. menziesii for A. micrantha. Selected recent specimens were subjected to molecular analysis. A key for the identification of all Belgian Amsinckia species is provided, along with SEM images of nutlets, as well as photographs of recently observed taxa.