精蛋白（Protamine）是一类结构简单的蛋白质，存在于成熟的精细胞中，与细胞核DNA结合在一起，如鱼精蛋白。呈碱性，含有较多的碱性氨基酸，不过缺少Trp和Tyr。

Protamines are small, arginine-rich, nuclear proteins that replace histones late in the haploid phase of spermatogenesis and are believed essential for sperm head condensation and DNA stabilization. They may allow for denser packaging of DNA in spermatozoon than histones, but they must be decompressed before the genetic data can be used for protein synthesis. However, in humans and maybe other primates, 10-15% of the sperm's genome is packaged by histones thought to bind genes that are essential for early embryonic development.