• Posidonia Bronn, 1828 † [Family: Pterioida (awaiting allocation)]
• Posidonia König, 1805 [Family: Posidoniaceae]
• Posidonia Sadykov, 1962 † (uncertain) [Family: Bivalvia (awaiting allocation)]
• Posidonia angustifolia Cambridge & Kuo, 1979
• Posidonia australis J.D. Hooker, 1858
• Posidonia coriacea Cambridge & Kuo
• Posidonia denhartogii Kuo & Cambridge, 1984
• Posidonia kirkmanii Kuo & Cambridge
• Posidonia kirkmannii Kuo & Cambridge, 1984 accepted as Posidonia kirkmanii Kuo & Cambridge
• Posidonia oceanica (Linnaeus) Delile, 1813
• Posidonia ostenfeldii den Hartog, 1970
• Posidonia robertsoniae Kuo & Cambridge, 1984
• Posidonia sinuosa Cambridge & Kuo, 1979
• Posidoniaceae Vines, 1895