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Human adenovirus species D (HAdV-D) contains two-thirds of all known HAdV types (116 in total) and is important as a vector in clinical applications. However, the broad tropism exhibited by several HAdV-D types poses challenges for their use as targeted gene delivery vectors. Since adenoviral tropism is largely governed by receptor usage, we aimed to determine the relative importance of known adenovirus receptors in mediating infection by different HAdV-D types. Here, we generated A549 single-cell CRISPR/Cas9 knockout clones of desmoglein 2 (DSG2), CD46, the coxsackievirus and adenovirus receptor (CAR), and cytidine monophosphate N-acetylneuraminic acid synthetase (CMAS; needed for biosynthesis of sialic acid-containing glycans), and assessed their relative importance for infection by 18 different HAdV-D types. We show that CD46 is the most important receptor for a majority of species D HAdVs. Minor changes in infection levels were noted with A549-ΔCAR and A549-ΔDSG2 cells, whereas A549-ΔCMAS cells displayed an increased susceptibility to infection. We proceed to show that HAdV-D types require CD46 for efficient attachment to A549 cells, and surface plasmon resonance analysis demonstrates that their hexon proteins bind CD46 in an avidity-dependent manner. Strategies to retarget HAdV-D vectors should thus consider hexon-CD46 interactions as a critical determinant of tropism, as CD46 is broadly expressed in vivo. These results increase our understanding of adenovirus-host interactions and will guide the development and targeting of vectors based on HAdV-D types. IMPORTANCE: Several human adenovirus species D (HAdV-D) types are currently used, or under development, as viral vectors for vaccines and gene delivery. However, the unusually broad tropism observed in many HAdV-D types limits their specificity and effectiveness as targeted vectors. Since tropism is largely governed by receptor usage, and previous studies have reported conflicting findings on receptor preferences within this species, clarifying receptor usage is essential. In this study, we systematically investigated receptor usage in 18 different HAdV-D types and identified CD46 as the primary receptor. Since CD46 is widely expressed across human tissues, our findings explain the broad cellular tropism of these viruses and provide valuable insight for the rational design and refinement of HAdV-D-based vectors.