密码哈希函数（英语：Cryptographic hash function），又译为加密哈希函数、密码散列函数、加密散列函数，是散列函数的一种。它被认为是一种单向函数，要由散列函数输出的结果，回推输入的数据是什么，是非常困难的。这种散列函数的输入数据，通常被称为消息（message），而它的输出结果，经常被称为消息摘要（message digest）或是摘要（digest）。

一个理想的密码哈希函数应该有四个主要的特性：

在信息安全中，有许多重要的应用，都使用了密码哈希函数来实作，例如数字签章，消息鉴别码。

A cryptographic hash function is a mathematical algorithm that maps data of arbitrary size to a bit string of a fixed size (a hash function) which is designed to also be one-way function, that is, a function which is infeasible to invert. The only way to recreate the input data from an ideal cryptographic hash function's output is to try a large number of possible inputs to see if they produce a match. Bruce Schneier has called one-way hash functions "the workhorses of modern cryptography". The input data is often called the message, and the output (the hash value or hash) is often called the message digest or simply the digest.