The invertebrate collection is a collection that was established in 2023 by reorganizing the invertebrate collections at NHMO. It includes parts of the former helminth and crustacean collections. The collection includes all invertebrate groups except Panarthropoda, Mollusca, Bryozoa, Brachiopoda, and Phoronida. In total, the collection is responsible for 25 major invertebrate taxa (23 are known as phyla and two as subphyla). Originating from the museum's research history, the collection has several different main focuses. One taxon of research interest is polychaete worms (Annelida). Another group is three major parasitic groups. Haptor worms (Monogenea, Gyrodactylus) and flukes (Digenea, Phyllodistomum) infecting fishes are two groups and roundworms (Nematoda, Elaphostrongylus) infecting deer (Cervidae) is another. Cnidarians and echinoderms also form large groups in the collection. In addition, many researchers over the years have collected other material from both freshwater and marine areas in Norway and several other countries. There is also material from several expeditions from the 19th and 20th centuries. The oldest material dates to the collecting activities of Michael Sars.The collection comprises approximately 15,000 catalogued objects. In addition, there are uncatalogued objects (approximately 8,000 specimens) and also unsorted material from various expeditions and projects. The majority of this is alcohol-preserved material (wet collections). Additionally, approx. 800 catalogued microscopy slides (there are also several thousand uncatalogued slides as reference material from project work) are part of the collection. Over 265 species are first descriptions (type material) with 410 specimens.All accessioned specimens have been digitized and are partly available on GBIF. The rest will soon be made available. The collection is used by the museum's researchers and students, and by researchers from Norway and abroad who either borrow material or visit the museum as guest researchers. The is a source for local, national and international research. In addition, objects in the collection are made available for DNA-based research such as genome sequencing. This will be particularly important in view of the new large, global genome projects and the fact that many species will only be possible to sequence from museum material. The latter is particularly demanding for material from wet collections.