Sergey Mergelyan (Armenian: Սերգեյ Մերգելյան; born 19 May 1928 in Simferopol, Crimea, Soviet Union; died 20 August 2008 in Los Angeles, USA; buried at the Novodevichie Memorial Cemetery in Moscow, Russia) was an Armenian scientist, an outstanding mathematician, who is the author of major contributions in Approximation Theory. The modern Complex Approximation Theory is based on Mergelyan's classical work.
He graduated from Yerevan State University in 1947. When he was just 20, in Moscow Steklov Mathematical Institute he was awarded the USSR Doctor of Science degree in mathematics in addition to his Ph.D. Up today this is an absolute record of getting the highest scientific degree (Doctor of Science) at such young age in former USSR and present Russia. In 1952 he was awarded USSR State Prize. When he was just 24 he became corresponding member of the Academy of Sciences of the USSR (now Russian Academy of Sciences), which, from the point of view of young age, is yet another absolute record among USSR scientists. He has been a symbol of a young scientist in former USSR. Indira Gandhi, among other famous people in USSR and abroad, has been a friend of Mergelyan from early 1950s. In 1978, after her official visit to Moscow, Gandhi had also a private visit to Yerevan just as a guest of Mergelyan.