• Olearia Herrmannsen, 1847 [Family: Turbinidae]
• Olearia Moench, 1802 [Family: Asteraceae]
• Oleinis F.E. Clements in F.E. Clements & Shear, 1931 accepted as Oleina Van Tieghem, 1887
• Oleria Hübner, 1816
• Olivaris Arango, 1878 (uncertain)
• Oluris von Heyden, 1826 (uncertain)
• Olyris Agassiz, 1846 (unaccepted)
• Oreacris Bolivar, 1911
• Otaris Buckton, 1903 (uncertain)
• Oxyaris Calmette, 1895 accepted as Oxyuris Rudolphi, 1803