Prince Joachim Viktor Wilhelm Leopold Friedrich Sigismund of Prussia (17 December 1891 – 6 July 1927) was a German World War I fighter pilot and member of the House of Hohenzollern. He was the son of Prince Friedrich Leopold of Prussia and Princess Louise Sophie of Schleswig-Holstein-Sonderburg-Augustenburg, married in 1916.
At Glienicke Castle, Prince Joachim Viktor Wilhelm Leopold Friedrich Sigismund was born to Prince Friedrich Leopold of Prussia and his wife Princess Louise Sophie of Schleswig-Holstein-Sonderburg-Augustenburg on 17 December 1891. He was their second child and eldest son; his siblings would come to include Princess Victoria Margaret, Prince Friedrich Karl, and Prince Friedrich Leopold.Like some other Hohenzollerns like Prince Heinrich of Prussia, Friedrich was greatly interested in aviation. In 1911, he began building an aeroplane at Glenicke Castle, with the hopes of trying it out the following spring. In 1917, he and his brother Friedrich Karl joined the German flying corps. Later that year, his brother died from war wounds.
On 27 April 1916, he married at Jagdschloss Klein-Glienicke in Berlin Princess Marie Louise of Schaumburg-Lippe (b. 10 February 1897, Oldenburg - d. 1 October 1938, Potsdam) (a daughter of Prince Friedrich of Schaumburg-Lippe and Princess Louise of Denmark).
They had two children:
He and his wife were great lovers of riding and horses, and he was considered one of the best horsemen in Germany. The couple spent most of their time raising and training horses at their Mecklenburg estate, as well as at their estate at Glienicke Castle near Potsdam. He and his wife were great social favorites, and Friedrich was popular with the German people.
On 5 July 1927 at age 35 at Lucerne, Switzerland, Frederich Sigismund fell from a horse. He was riding in an international tournament; while doing a difficult jump, he fell and his foot got caught in a stirrup. Before he was able to free himself, the horse trod his chest multiple times, breaking five ribs and causing other injuries. He was rushed to a nearby hospital, where he died the following day from his injuries.
His body was brought back to Potsdam, where a ceremonial funeral was held. Important members of the Hohenzollern dynasty attended, including former Crown Prince Wilhelm and his brother Prince Eitel Friedrich of Prussia. He was buried at Glienicke Palace, next to his sister Princess Victoria Margaret of Prussia.