黑索金（英文：Hexogen），一种高能炸药，学名环三亚甲基三硝胺（cyclotrimethylenetrinitramine），其通称RDX为Research Department explosive的缩写。

原设想用于医药，后因具有良好的爆炸性能（比硝化甘油强，是TNT的158%）被发展作炸药用途。爆轰感度良好，起爆容易，是综合性极佳的炸药。此外，还用作毒鼠药。

1899年德国在发表的专利中首次叙述制造黑索金，当时并没有提出作为炸药而是推荐作为医用药物，后来的发表的专利中提出用于制造无烟发射药。

RDX, an initialism for Research Department explosive, is an explosive nitroamine widely used in military and industrial applications. It was developed as an explosive which was more powerful than TNT, and it saw wide use in World War II. RDX is also known as Research Department Formula X, cyclonite, hexogen (particularly in German and German-influenced languages), and T4. Its chemical name is cyclotrimethylenetrinitramine; name variants include cyclotrimethylene-trinitramine and cyclotrimethylene trinitramine.