硬件抽象层（HAL, Hardware Abstraction Layer），是抽象层的一种，是实作于硬件和运行于该电脑的软件之间的一种特殊软件。它的功用是将硬件方面的不同，隐藏并抽离于操作系统的核心之中。如此一来核心模式的代码就不必因为硬件的不同而需要修改。所以硬件抽象层可增进软件的可移植性。

之所以有硬件抽象（Hardware abstraction）这个概念，是由于数字电脑具体的硬件（Hardware）操作相当繁杂，因此将具体的硬件操作抽象化简，避免由于直接以具体的机器码（Machine code）撰写程序，而在将程序移植到不同硬件时，需要重写整个程序。其概念与目的，类似于数据结构（Data structure）中的抽象数据类型(Abstract data type)，皆为保护程序免受变化的冲击。

Hardware abstractions are sets of routines in software that emulate some platform-specific details, giving programs direct access to the hardware resources.

They often allow programmers to write device-independent, high performance applications by providing standard Operating System (OS) calls to hardware. The process of abstracting pieces of hardware is often done from the perspective of a CPU. Each type of CPU has a specific instruction set architecture or ISA. The ISA represents the primitive operations of the machine that are available for use by assembly programmers and compiler writers. One of the main functions of a compiler is to allow a programmer to write an algorithm in a high-level language without having to care about CPU-specific instructions. Then it is the job of the compiler to generate a CPU-specific executable. The same type of abstraction is made in operating systems, but OS APIs now represent the primitive operations of the machine, rather than an ISA. This allows a programmer to use OS-level operations (e.g. task creation/deletion) in their programs while retaining portability over a variety of different platforms.