Mycoplasmas are regularly isolated from the upper respiratory tract of predatory birds; however, most of these Mycoplasma isolates remain unidentified. A cohort of such unidentified Mycoplasma strains (n = 42) recovered from birds of the Accipitridae family was subjected to a comprehensive taxonomic study. All strains grew well in modified Hayflick's medium, and colonies exhibited typical fried egg morphology. The strains neither produced acid from sugar carbon sources nor hydrolysed arginine or urea. Analyses of 16S rRNA gene, 16S23S intergenic spacer, and partial rpoB gene sequences placed the strains within the Mycoplasma (M.) synoviae cluster (Hominis group) with M. verecundum and M. seminis being their closest relatives. Phylogenetic trees inferred from 16S rRNA and rpoB gene sequences subdivided the 42 strains into five strain clusters. MALDI-ToF mass spectrometry allowed the differentiation of one strain group from the others but failed to distinguish the remaining four strain groups. Genome and proteome similarity metrics (ANIb, ANIm, TETRA, dDDH, AAI) and phylogenomic analysis provided solid evidence that the strains examined are indeed representatives of five hitherto unclassified species of genus Mycoplasma for which the names Mycoplasma aquilae sp. nov., Mycoplasma paraquilae sp. nov., Mycoplasma haliaeeti sp. nov., Mycoplasma milvi sp. nov., constituting the newly defined Mycoplasma aquilae complex, and Mycoplasma razini sp. nov. are proposed, with their designated type strains 1449T (ATCC BAA-1896T = DSM 22458T), 654T (DSM 113738T = NCTC 14855T), VS42AT (DSM 113741T = NCTC 14856T), Z331BT (DSM 113740T = NCTC 14858T), and 005VT (DSM 113739T = NCTC 14838T), respectively.