This article is devoted to the life and various activities of the outstanding diplomat Prince Alexey B. Lobanov-Rostovsky (1824–1896). The name of Lobanov-Rostovsky was not mentioned in the academic literature until the first decade of the 21st century. Then Lobanov began to be remembered thanks to the efforts of his descendant Prince Nikita D. Lobanov-Rostovsky, who initiated a number of studies about the prominent diplomat. A fundamental monograph on Prince Lobanov-Rostovsky has now been prepared. His international activity as Ambassador Extraordinary and Plenipotentiary took place during some of the most difficult political periods of the time: in Constantinople (1859–1863 and 1878–1879), London (1879–1882) and Vienna (1882–1895). He always managed to solve the most pressing problems using skillful diplomatic tools. He was appointed Deputy Minister of the Ministry of Internal Affairs during the challenging period of restructuring of social and public institutions in Russia. It was the era of the so called Great Reforms of Emperor Alexander II. The position was offered to the Prince on account of his superior intellect, strategic foresight and tactical flexibility. During his 11 years in the post (1867–1878), Prince Lobanov-Rostovsky often performed the duties of a minister. During this time, the legal norms of the state and its relations with society significantly improved. In 1870, Alexey B. Lobanov-Rostovsky received the honorary position of State-Secretary of His Imperial Majesty, that is, the Emperor's personal speaker, a position he held until the end of his life. Both Emperor Alexander II and Nicholas II treated Lobanov-Rostovsky with a special warmth. Lobanov-Rostovsky managed to conclude the Russian-Turkish final Peace Treaty of 1879, which put an end to the war between the two countries. This agreement gave Russia significant moral and material results and marked the beginning of the autonomous Principality of Bulgaria, the first steps towards Bulgarian statehood. Lobanov-Rostovsky served as Foreign Minister for 18 months (1895–1896), during which time he brought Russia significant results on the world stage and was highly appreciated both in Russia and around the world. This article talks about the different sides of the prince’s extraordinary personality. A true polymath, proficient in the Russian antiquity, he became a bibliophile, collector, genealogist and historian. He wrote carefully considered commentaries on the historical documents he discovered, and for 14 years (1871–1885) he systematically published his work in history journals. This article examines memoir entries of Lobanov-Rostovsky’s contemporaries about the diplomat, as well as the latest research about him.