A new water-penny beetle, Succinumanax birmaniasis gen. et sp. nov., is described based on two well-preserved larvae from mid-Cretaceous Burmese amber. They represent the oldest fossil record of Psephenidae, and show a high similarity in morphology with fossils from the Eocene Messel pit, Germany. The new phylogenetic analysis demonstrates that S. birmaniasis and the Messel specimen can be placed in the subfamily Eubrianacinae. The structure of the gills and functional spiracles indicates that the respiration system of the larvae of S. birmaniasis was well-developed. Specifically, their medial suture is well-developed, which might be a plesiomorphic character. Evolutionary relationships and biogeographical distribution patterns are discussed, the evidence supports a general dispersal trend from Southeast Asia to Europe. Furthermore, S. birmaniasis provides new insights into the taphonomy of similar organisms, in this process a huge amount of resin and fast embedding of specimens are important factors. Together with other taxa which have been found in Burmese amber, the current report provides a more detailed view on the palaeoenvironmental setting of the mid-Cretaceous Burmese amber forest.