During a survey of odonates along the river Wadi Boulahdaid in the north-east of Algeria, a new population of the large red damselfly, Pyrrhosoma cf. nymphula,was recorded. This stream had not been explored in previous odonatological studies in Algeria. The population displayed a range of reproductive behaviours, from copulation and oviposition to territoriality, which suggests local establishment. This finding adds a new locality within the previously known North African range of this taxon, which runs from northern and western Morocco to Tunisia through the Rif Mountains, the High and Middle Atlas and the Tell Atlas orographic system. It contributes to an improved understanding of the North African odonate fauna.