并行计算（英语：parallel computing）一般是指许多指令得以同时进行的计算模式。在同时进行的前提下，可以将计算的过程分解成小部份，之后以并行方式来加以解决。

电脑软件可以被分成数个运算步骤来运行。为了解决某个特定问题，软件采用某个算法，以一连串指令运行来完成。传统上，这些指令都被送至单一的中央处理器，以循序方式运行完成。在这种处理方式下，单一时间中，只有单一指令被运行(processor level: 比较微处理器，CISC, 和RISC，即流水线Pipeline的概念，以及后来在Pipeline基础上以提高指令处理效率为目的的硬件及软件发展，比如branch-prediction, 比如forwarding，比如在每个运算单元前的指令堆栈，汇编进程员对programm code的顺序改写)。平行运算采用了多个运算单元，同时运行，以解决问题。

Parallel computing is a type of computation in which many calculations are carried out simultaneously, operating on the principle that large problems can often be divided into smaller ones, which are then solved at the same time. There are several different forms of parallel computing: bit-level, instruction-level, data, and task parallelism. Parallelism has been employed for many years, mainly in high-performance computing, but interest in it has grown lately due to the physical constraints preventing frequency scaling. As power consumption (and consequently heat generation) by computers has become a concern in recent years, parallel computing has become the dominant paradigm in computer architecture, mainly in the form of multi-core processors.