Rubidium oxide is a chemical compound. Its chemical formula is RbO. It is a yellow solid. It reacts vigorously with water to produce rubidium hydroxide, a very strong base. It is made by reduction of rubidium nitrate using rubidium metal. It can also be made by reduction of rubidium hydroxide with rubidium metal. It reacts with hydrogen to disproportionate it into rubidium hydroxide and rubidium hydride.