阿普第期(Aptian)是白垩纪的第五个时期，时间为125.0 ± 1.0 百万年前至 112.0 ± 1.0 百万年前。

命名自法国市镇阿普特（Apt）。

阿普第期位于巴列姆期之后，阿尔布期之前。

The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous epoch or series and encompasses the time from 125.0 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), approximately. The Aptian succeeds the Barremian and precedes the Albian, all part of the Lower/Early Cretaceous.