We present, to our knowledge, the first complete genome sequence of a waterfowl aviadenovirus, goose adenovirus (GoAdV) strain P29, and an analysis of its genetic content in comparison with five published aviadenovirus genome sequences. Of the 35 genes predicted to encode functional proteins, the central region of the genome contains 19 (IVa2 to fiber-2) that were inherited from the ancestor of all known adenoviruses. Of the remaining genes, nine have orthologues only in aviadenoviruses and seven lack orthologues in any adenovirus. We also obtained limited sequence data for a pathogenic GoAdV strain D1036/08. Phylogenetic analyses placed the two GoAdV strains monophyletically in the genus Aviadenovirus. We propose designating strains P29 and D1036/08 as GoAdV-4 and GoAdV-5, respectively.