海百合是一种始见于石炭纪的棘皮动物，生活于海里，具多条腕足，身体呈花状，表面有石灰质的壳。

古生代石炭纪时，海百合数量极庞大，品种繁多，可归类在「海百合亚门」之下的多个纲目下。牠们跟苔藓虫和腕足动物在海底形成草地般的大面积覆盖面，留下许多化石（早侏罗纪的一种海百合Lobothyris subgregaria就是典型例子）。后因「二叠纪、三叠纪灭绝事件」，90%的海洋物种灭绝，海百合也迅速退出历史舞台。

现生种的海百合纲被重新发现时，是在深水海域中，所以初期人们以为牠们只能在深海生存。后来发现，原来不论浅海或深海、热带珊瑚礁或高纬度海域，都能发现其踪迹。

Crinoids are marine animals that make up the class Crinoidea of the echinoderms (phylum Echinodermata). Crinoidea comes from the Greek word krinon, "a lily", and eidos, "form". They live both in shallow water and in depths as great as 9,000 meters (30,000 ft). Sea lilies refer to the crinoids which, in their adult form, are attached to the sea bottom by a stalk. Feather stars or comatulids refer to the unstalked forms.