确定性算法（英语：deterministic algorithm）是计算机算法的一类。如果以算法的每一步骤是否确定来分类，计算机算法可以分为确定性算法和随机化算法。

In computer science, a deterministic algorithm is an algorithm which, given a particular input, will always produce the same output, with the underlying machine always passing through the same sequence of states. Deterministic algorithms are by far the most studied and familiar kind of algorithm, as well as one of the most practical, since they can be run on real machines efficiently.