This study describes Renicola websterae n. sp., a newly identified kidney fluke (Renicolidae: Trematoda) infecting two penguin species from New Zealand, the little blue penguin (Eudyptula novaehollandiae) and the Fiordland crested penguin (Eudyptes pachyrhynchus). Morphological and molecular analyses, including phylogenies based on cox1 and 28S genes, confirmed the distinctiveness of R. websterae. Key morphological features were discerned to be statistically comparable across five developmental stages, facilitating detailed characterization even in less mature specimens. A putative second, genetically distinct Renicola sp. was identified in Fiordland crested penguins and intermediate fish hosts, indicating a potential trophic link, and partly completing the known life cycle. We discuss the fact that kidney flukes have only been found in these two penguins and not in other New Zealand species, and the ecological and host-specificity factors likely influencing parasite distribution. This work represents the first record of a named Renicola species from New Zealand and only the second species found in penguins worldwide.