物候学（英语：phenology 源于希腊文：phainomai(φαινομαι-显示、见现)）为研究气候与生态事件（特指生物的某现象）互相时间关系之学问。这门科学主要关心生物事件之变化在年循环里出现的日期。例如：《夏小正》里提及的「正月启蛰，雁北乡」、「七月秀雚苇，狸子造肆」等。

在生态学科学文献里，这个辞也普遍应用在其他较短时段的生物现象，例如季节性的物候：某物种开始发生于4四月，于9月死亡（消失）。

由于生物生长的现象常常受到温度的影响，且敏感，因此温度造成物候变化成为一个观察历史气候记录的重要指标，尤其是气候变迁及全球暖化的研究议题。例如：欧洲已借由过去500年来的葡萄产量，创建一垂直温度纪录。 在无法利用精确仪器实际量测全球暖化的现象时，物候学的研究提供了一个精准的记录。

Phenology is the study of periodic plant and animal life cycle events and how these are influenced by seasonal and interannual variations in climate, as well as habitat factors (such as elevation). The word is derived from the Greek φαίνω (phainō), "to show, to bring to light, make to appear" + λόγος (logos), amongst others "study, discourse, reasoning" and indicates that phenology has been principally concerned with the dates of first occurrence of biological events in their annual cycle. Examples include the date of emergence of leaves and flowers, the first flight of butterflies and the first appearance of migratory birds, the date of leaf colouring and fall in deciduous trees, the dates of egg-laying of birds and amphibia, or the timing of the developmental cycles of temperate-zone honey bee colonies. In the scientific literature on ecology, the term is used more generally to indicate the time frame for any seasonal biological phenomena, including the dates of last appearance (e.g., the seasonal phenology of a species may be from April through September).