肉鳍鱼（Sarcopterygii）是硬骨鱼类的一个纲。此类鱼的特点是鱼鳍中有一个中轴骨，在前鳍的基部上有明显的肌肉组织与分开的两片腹鳍，和之后两栖动物和四足类动物的演化有直接的关联性。此纲之下包括腔棘鱼亚纲(Actinistia)、肺鱼形亚纲(Dipnomorpha)和四足形亚纲(Tetrapodomorpha)。 其中的腔棘鱼曾被认为已完全灭绝，直到1938年才在非洲东南海域深海捕捉到活体，之后并在印度等地区多次被发现而证实仍然存活于深海中。目前仅存一目二种，即矛尾鱼，被认为是鱼类中的活化石。

The Sarcopterygii /ˌsɑːrkɒptəˈrɪdʒi.aɪ/ or lobe-finned fish (from Greek σαρξ sarx, flesh, and πτερυξ pteryx, fin) – sometimes considered synonymous with Crossopterygii ("fringe-finned fish", from Greek κροσσός krossos, fringe) – constitute a clade (traditionally a class or subclass) of the bony fish, though a strict cladistic view includes the terrestrial vertebrates. The living sarcopterygians are the coelacanths and lungfish; additionally, all tetrapods are sarcopterygians or descendants of them.