A Rubus. A huge and complicated genus so I would never attempt a more precise id than 'it's a blackberry'.

Rubus, especially the blackberries, presents some of the most difficult species-level problems, because of polyploidy, apomixis, and hybridization. As a result, differences of opinion on the number of species to be recognized from a given region can vary tremendously …. Cultivars of blackberries and raspberries are grown for their edible fruit, and other Rubus taxa are grown for their ornamental value. Cultivars of blackberries have parentages or origins that include species native to North America and Europe, as well as red raspberry

www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=128837