箭石类动物（学名：Belemnoida），旧作箭石下纲，是一种已经灭绝头足纲生物的分支，生活在泥盆纪至白垩纪之间。箭石在许多方面都与现代的鱿鱼相当接近，而且与现代的乌贼关系密切。箭石也拥有墨囊，不过牠们有10条大约相同长度的触腕，其中并没有特别长的触腕。

The name "belemnoid" comes from the Greek word βέλεμνον, belemnon meaning "a dart or arrow" and the Greek word είδος, eidos meaning "form".

Belemnoids are an extinct group of marine cephalopod, very similar in many ways to the modern squid and closely related to the modern cuttlefish. Like them, the belemnoids possessed an ink sac, but, unlike the squid, they possessed ten arms of roughly equal length, and no tentacles. The name "belemnoid" comes from the Greek word βέλεμνον, belemnon meaning "a dart or arrow" and the Greek word είδος, eidos meaning "form".