落叶植物，是植物学中一个常见名词，与常绿植物相对，在一年中有一段时间叶片将完全脱落，枝干将变得光秃秃的没有叶子。落叶性出现的原因如季节及气候有明显关系。由于在秋冬季节温度一般较低，气候亦较干旱及易有缺水情况，致使植物生长停止，叶全部脱落，于翌年再长出嫰叶。除了于热带及部分温带地区生长的物种较多为常绿性外，其余植物皆为落叶性或半落叶性。半落叶性表示植物同样受秋冬季节气候影响导致生长抑缓，其叶则有部分脱落。

一般被子植物门当中是落叶性的植物较多，而松柏门中，则只有落羽杉属（Taxodium）、落叶松属（Larix）、水杉属（Metasequoia）和水松属（Glyptostrobus）是落叶性。而银杏门的银杏也是落叶树。

Deciduous means "falling off at maturity" or "tending to fall off", and it is typically used in order to refer to trees or shrubs that lose their leaves seasonally (most commonly during autumn) and to the shedding of other plant structures such as petals after flowering or fruit when ripe. In a more general sense, deciduous means "the dropping of a part that is no longer needed" or "falling away after its purpose is finished". In plants it is the result of natural processes. "Deciduous" has a similar meaning when referring to animal parts, such as deciduous antlers in deer or deciduous teeth, also known as baby teeth, in some mammals (including humans).