Alexander was the son of Alexander, Prince of Hesse and his morganatic wife Julia von Hauke. Julia was created Princess of Battenberg and the title was inherited by her sons. His brother Ludwig became the 1st Marquess of Milford Haven.
When, under the Treaty of Berlin (1878), Bulgaria became an autonomous principality under the suzerainty of the Ottoman Empire, the Tsar Alexander II, Alexander's uncle, recommended his nephew to the Bulgarians as a candidate for the newly-created throne, and the Grand National Assembly unanimously elected Prince Alexander as Prince of Bulgaria on 29 April 1879. He became the first Knayz or Prince of a modern Bulgaria reigning from 29 April 1879 to 7 September 1886. He was ill prepared to assume such a task as he had no training in government.
After political uphevels, including suspending the country's constitution and the Revolution of Plovdiv, Alexander resigned. He was given the title of Count of Hartenau and retired to Graz.
On 6 April 1889 in France, he married an actress, Joanna Maria Louise Loisinger. They were the parents of Asen, and Tsvetana.
Joanna Maria Louisa Loisinger Battenberg