Rubidium hydrogen sulfate, sometimes referred to as rubidium bisulfate, is the half neutralized rubidium salt of sulfuric acid. It has the formula RbHSO₄.

It may be synthesised with water and a stoichiometric amount of rubidium disulfate. Reaction takes place where there is no humidity:

There is another method of creation. It is similar to the synthesis of sodium sulfate and potassium sulfate. This reaction requires rubidium chloride and a little bit of warm sulfuric acid. Some hydrogen chloride is also produced during the reaction.

It is a hygroscopic compound. It has a monoclinic crystal structure, its structure is P2₁/n. Dimensions of the unit cell are: a = 1440 pm, b = 462.2 pm, c = 1436 pm and β = 118.0°. Its crystals are isomorphs with ammonium hydrogen sulfate crystals.

Its standard enthalpy is −1166 kJ/mol. During its dissolution in water, there is 15.62 kJ/mol energy produced.

After warming up it decomposes to rubidium disulfate and water:

Like potassium and caesium, rubidium has another hydrogen sulfate compound as well: Rb₃H(SO₄)₂.