丙二酰脲，又称巴比妥酸（Barbituric acid），化学名：2,4,6-嘧啶三酮。

一种白色无臭结晶体，难溶于冷水和乙醇，溶于热水和乙醚。通常含有两分子结晶水。在空气中易风化。水溶液呈强酸性。可以与金属反应生成盐类。

Barbituric acid or malonylurea or 6-hydroxyuracil is an organic compound based on a pyrimidine heterocyclic skeleton. It is an odorless powder soluble in water. Barbituric acid is the parent compound of barbiturate drugs, although barbituric acid itself is not pharmacologically active.