Andrei Sergeyevich Famintsyn (Russian: Андрей Серге́евич Фаминцын) (June 17 (O.S. June 29), 1835, Moscow – December 8, 1918, Petrograd) was a Russian botanist, public figure, and academician of the Petersburg Academy of Sciences (1884).
Famintsyn attended Saint Petersburg State University and studied under Russian fungal expert Lev Semionovich Tsenkovsky. In 1861, he continued his scientific career as a teacher at his alma mater and became a professor (1867-1889). In 1890, Famintsyn founded and headed the Laboratory of Plant Anatomy and Physiology of the Academy of Sciences (today's Timiryazev Institute of Plant Physiology of the Russian Academy of Sciences). Famintsyn is considered the founding father of the Petersburg school of plant physiologists (Ivan Borodin, Alexander Batalin, Dmitry Ivanovsky and others). In 1887, he authored the first Russian textbook on plant physiology. His major works were dedicated to photosynthesis and plant metabolism. He was the first to use artificial light for plant growing and research (1868). Famintsyn showed that carbon dioxide conversion by plants and formation of starch may occur under artificial lighting. Together with O. Baranetsky, he was the first to separate the green algae cells from lichens. Famintsyn discovered the symbiosis of algae with radiolarias and developed a theory of symbiogenesis. In 1906-1909, he was the president of the Free Economic Society. In 1915, Famintsyn was elected honorary president of the Russian Botanic Society.