趋性（英语：taxis，或称为趋向性）是一生物(或细胞)天生的行为反应，指其对一指向性刺激(由特定方向给的刺激)，而会有趋进(正趋性)或远离(负趋性)刺激源的动作。趋性和向性不同，生物的趋性有移动性且显现出趋进至远离刺激源指向运动(Kendeigh, 1961)。例如眼虫属的鞭毛原生动物会趋向光源。这里，指向性刺激为光，而其动作为趋向光。此一反应或行为称做正趋光性，而趋光性正是指对光刺激的反应。有许多其他类型的趋性已经被发现了，详列如下：

依据感觉器官的不同，趋性可以被分为屈曲趋性－一生物持续感觉环境以决定刺激的方向，对称趋性－以两个感觉器官来决定刺激方向，以及趋激性－和对称趋性相似，但只以单一器官来创建其动作。

A taxis (plural taxes /ˈtæksiːz/, from the Ancient Greek τάξις, meaning "arrangement") is the movement of an organism in response to a stimulus such as light or the presence of food. Taxes are innate behavioral responses. A taxis differs from a tropism (turning response, often growth towards or away from a stimulus) in that the organism has motility and demonstrates guided movement towards or away from the stimulus source. It is sometimes distinguished from a kinesis, a non-directional change in activity in response to a stimulus.