内存阶层是在电脑架构下保存系统阶层的排列顺序。每一层于下一层相比都拥有较高的速度和较低延迟性，以及较小的容量（也有少量例外，如AMD早期的Duron CPU）。

大部分现今的中央处理器的速度都非常的快。大部分程序工作量需要内存访问。由于缓存的效率和内存传输位于阶层中的不同等级，所以实际上会限制处理的速度，导致中央处理器花费大量的时间等待内存I/O完成工作。

大部分电脑中的内存阶层如下：

In computer architecture the memory hierarchy is a concept used when discussing performance issues in computer architectural design, algorithm predictions, and the lower level programming constructs such as involving locality of reference. The memory hierarchy in computer storage distinguishes each level in the hierarchy by response time. Since response time, complexity, and capacity are related, the levels may also be distinguished by their performance and controlling technologies.