In Europe, mosquito-related public health concerns are growing due to the increasing spread of invasive mosquito species and the recent emergence of mosquito-borne arboviruses. A vital backbone in the assessment of these issues is detailed knowledge of the mosquito fauna, i.e. regional mosquito inventories. It was therefore decided to intensify nationwide investigations on the occurrence and distribution of mosquitoes in Germany in order to update old records and to detect possible faunal changes. This paper is focussing on a densely populated metropolitan region, the federal state of Hamburg and its adjacent environs, taking two historical baseline inventories into consideration, spanning almost 100 years of mosquito research in Hamburg. In the period between 2010 and 2014, more than 10,000 juvenile, neonate and adult mosquito specimens were sampled and trapped at 105 sites in Hamburg and its environs, of which about 60% have been identified to species level, resulting in a total of 33 recorded species. Of these, Anopheles algeriensis, Culex modestus, Ochlerotatus caspius, Ochlerotatus nigrinus and Ochlerotatus sticticus are new to the area. The most common species in Hamburg are Culex pipiens/torrentium and Ochlerotatus annulipes/cantans. In contrast, two previously common species, Anopheles atroparvus and Ochlerotatus excrucians, were not detected. Despite substantial environmental changes due to reconstruction, urbanisation and renaturation in the Hamburg metropolitan region in recent decades, there has been remarkably little change within the mosquito fauna during the last century.