Page Corps
Svyatopolk-Mirsky was born in Vladikavkaz into the prominent Svyatopolk-Mirsky family. He was the only son of the general Dmitry Ivanovich Svyatopolk-Mirsky and Georgian Princess Sofia Orbeliani. Pyotr was educated at Page Corps, graduating in 1874 with first-class honours, and was appointed Page of the Chamber. In 1875, he became a cornet at "Her Empress Leib-Guards Hussars". He was the father to literary historian D. S. Mirsky.