羽齿兽（Ptilodus），中上古时代的哺乳动物，已于冰河时期灭绝之动物属项。该动物为草食动物，最大特征在于牙齿拥有啮齿动物的长门牙，另外也有尖锐的剪齿。而最主要的咀嚼为后颚的臼齿，据研考推算，后颚亦拥有强而有力的咀嚼肌肉。

Ptilodus is a genus of mammals from the extinct order of Multituberculata, and lived during the Paleocene in North America.

Ptilodus was a relatively large multituberculate of 30 to 50 centimetres (12 to 20 in) in length, which is about the same size as a squirrel. Its feet, legs and long tail suggest it was a good climber, so it very possibly led a squirrel-like lifestyle.