The Mugiliformes are a taxon of marine, estuarine and freshwater fishes comprising 27 genera and 79 species. They are a dominant group in most regions where they occur and are commercially important for fisheries and aquaculture. While the ecology of mugiliforms is well investigated, multiple questions on their morphology, phylogeny and taxonomy remain. The last morphological studies featuring the Mugiliformes date back almost 20 years and the evolution of characters within this taxon are yet to be examined. Meanwhile, recent molecular analyses provided new insights into the phylogenetic position of mugiliforms as well as their taxonomy. However, these studies were not able to sufficiently resolve the phylogenetic intra- and interrelationships of mugiliforms. Many new phylogenetic hypotheses have been postulated of which the most conclusive assigned the Mugiliformes to the Ovalentaria in unresolved relationships to multiple other taxa. This dissertation generally focuses on the phylogenetic intra- and interrelationships of the Mugiliformes using different morphological approaches and analysing a wide spectrum of mugiliform and possible closely related taxa. The evolution of the mugiliform skeleton is examined and discussed in the light of recent phylogenetic hypotheses and the larval development. Furthermore, previously suggested relationships of mugiliforms and atherinomorphs, which were based on morphological data, are revised based on newly gathered data. Lastly, the latest and most extensive molecular-genetic hypothesis positioning the Mugiliformes within the Ovalentaria is evaluated on the basis of morphological data.