Hydrazine monohydrobromide (hydrazinium bromide) is a hydrobromide salt of hydrazine. It has been prepared by adding aqueous hydrobromic acid to aqueous hydrazine. Its crystal structure has been investigated. It participates in the synthesis of 2-(2′-furoyl)-4(5)-(2′-furanyl)-1H-imidazole (FFI). It is formed as an intermediate during the formation of phosphaminimides from hydrazide derivatives. The fumes from the pyrolysis of hydrazine monohydrobromide soldering flux have been reported to cause dermatitis.