Technical Abstract: Black swallow-wort, Vincetoxicum nigrum (L.) Moench, is a non-indigenous species that is highly invasive over large areas in the U.S., especially in the northeastern U.S. and southeastern Canada where it displaces desirable vegetation in upland natural areas, old fields, and landscape settings. Efforts have been underway to discover biological control agents of black swallow-wort across its native range of southern France, the Iberian Peninsula, Portugal, and northern Italy. Surprisingly little or no disease damage has been reported from black swallow-wort, probably becauseit produces alkaloids with antimicrobial activity. The occurrence of a stem rust, Cronartium flaccidum, was reported in 1918 in Spain and Portugal, on swallow-wort under the species name C. asclepiadum, which now includes both black and white swallow-wort species. In 2011, we found in the vicinity of Aleppo pines in southern France several black swallow-worts with orange yellow pustules of rust on the underside of leaves. Observed morphological features of these pustules were uredinia that eventually formed telia and which were consistent with those of C. flaccidum found on white swallow-wort in Finland and on pines in Italy. Molecular characterization using DNA sequencing of internal transcribed spacer regions confirmed the identification of this rust. This is the first report of occurrence of telia and uredinia of the two-needle pine stem rust on black swallow-wort definitively identified in France.