Additions to the Floristic Catalogue of the Province of Soria (Spain), III: Chorologic extensions at the Iberian System and Ebro Valley. Here we present 39 taxa corresponding to rare vascular plants which had not previously been recorded for Soria province, such as Apium inundatum, Camphorosma monspeliaca subsp. monspeliaca, , Colchicum triphyllum, Crupina crupinastrum, Blackstonia imperfoliata, Isoetes setaceum, Helianthemum marifolium, Najas marina, etc. Six out of these aforementioned ones, mean a novelty for the flora of Castilla y León region, such as Centaurea boissieri subsp. pinae, Colchicum triphyllum, Erysimum ruscinonesis, Gypsophila pilosa, and Helianthemum mariifolium. Some of them are very scarce in Castilla y León region or even in the Iberian Peninsula, and are threatened or protected. For all of them enlarge previously known distribution areas are enlarged or their delimitations are improved.