核酸酶（英语：nuclease）是以核酸为底物，催化磷酸二酯键水解的一类酶。

• 核酸被降解为低聚核苷酸或单核苷酸。

A nuclease is an enzyme capable of cleaving the phosphodiester bonds between the nucleotide subunits of nucleic acids. Older publications may use terms such as "polynucleotidase" or "nucleodepolymerase".

Nucleases are usually further divided into endonucleases and exonucleases, although some of the enzymes may fall in both categories. Well known nucleases are deoxyribonuclease and ribonuclease.