As the globally dominant group of pollinators, bees provide a key ecosystem service for natural and agricultural landscapes. Their corresponding global decline thus poses an important threat to plant populations and the ecosystems they support. Bee conservation requires rapid and effective tools to identify and delineate species. Here, we apply DNA barcoding to Irish solitary bees as the first step towards a DNA barcode library for European solitary bees. Using the standard barcoding sequence, we were able to identify 51 of 55 species. Potential problems included a suite of species in the genus Andrena, which were recalcitrant to sequencing, mitochondrial heteroplasmy and parasitic flies, which led to the production of erroneous sequences from DNA extracts. DNA barcoding enabled the assignment of morphologically unidentifiable females of the parasitic genus Sphecodes to their nominal taxa. It also enabled correction of the Irish bee list for morphologically inaccurately identified specimens. However, the standard COI barcode was unable to differentiate the recently diverged taxa Sphecodes ferruginatus and S. hyalinatus. Overall, our results show that DNA barcoding provides an excellent identification tool for Irish solitary bees and should be rolled out to provide a database for solitary bees globally.