Pyotr Alexandrovich Chikhachyov, last name also spelled Chikhachev or Tchihatchev (Russian: Пётр Алекса́ндрович Чихачёв; 23 December 1808 – 13 October 1890) was a Russian naturalist and geologist who was admitted into the Russian Academy of Sciences in 1876 as an honorary member. He authored geographical and geological descriptions of the Altai, Xinjiang (1845), and Asia Minor (1853-1869). One of the Altai mountain ranges is named after him.
He was born in the Large Gatchina palace, the summer residence of the dowager empress Maria Fyodorovna. His father was Alexander Petrovich Chikhachyov, a retired colonel of the Preobrazhensky regiment. Getting home education in Tsarskoye Selo, under the direction of lyceum professors, Chikhachyov finished his education abroad, attending the lectures of famous geologists and mineralogists, and then worked in Paris. Not a professional scientist, Chikhachyov, with sufficient money and scientific preparation, could completely give himself up to his interest in scientific expeditions and research. These produced essential scientific results, due to the observation of their author and careful treatment of the scientific material collected during expeditions, to which Chikhachyov attracted prominent specialists in different fields.
Chikhachyov's independent scientific activity began in 1841, when he published geological descriptions of Monte Gargano in South Italy and the environs of city of Nice. In 1842, he published a geological description of the southern provinces of the Neapolitan kingdom.