Sergei Yakovlevich Lemeshev (Russian: Серге́й Я́ковлевич Ле́мешев; 10 July [O.S. 27 June] 1902 – 27 June 1977) was a Soviet and Russian opera singer and director. People's Artist of the USSR (1950).

Lemeshev was born into a peasant family, and his father wanted him to become a cobbler. In 1914, he left a parish school and was sent to be trained to make shoes in Saint Petersburg. In 1917, he graduated from school in Tver, where he received vocal training. He began first at a local workers' club and later moved to Moscow.

Between 1921 and 1925, he studied at the Moscow Conservatory with Nazari Raisky. In 1924, he sang in the opera studio of Konstantin Stanislavski. From 1926 and 1931, he sang in the theatres of Sverdlovsk, Harbin, and Tbilisi.

In 1931 Lemeshev was invited to the Bolshoi Theatre, made his debut and eventually became the theatre's soloist. His lyrical tenor of an unusually soft and light timbre almost at once brought him love and popularity among admirers of the operatic art. Nevertheless, Lemeshev was a great worker and worked hard to develop each of his opera roles. His vocal and artistic qualities, evident to every listener, are beauty of timbre, musicality, effortlessness of vocal production, expressiveness, very clear diction and incredible pianissimo. The best years of his operatic career were from 1931 to 1942. He was also an outstanding concert singer and a brilliant performer of traditional Russian folk songs. In 1938, he became the first artist to sing all 100 romances by Tchaikovsky in 5 concerts. Folk songs broadcast on the radio further sealed his stature as a truly national singer.

The beginning of the Great Patriotic War was crucial for Lemeshev; during one evacuation he caught a very bad cold which resulted in two attacks of pneumonia, complicated by pleurisy and tuberculosis of the right lung. He was treated with artificial pneumothorax, which induced the therapeutic collapse of one lung. Although singing was forbidden, he adapted by being more conscious and sensitive with regard to his technique, and continued to sing with one lung from 1942 to 1948, when the other lung was also artificially collapsed and re-inflated. During that period he recorded Lakmé, The Snow Maiden, Les pêcheurs de perles, Mozart and Salieri and pieces from operas like The Barber of Seville and Rigoletto.

In 1947, he toured and performed at the Berlin State Opera. Along with his friendly rival, tenor Ivan Kozlovsky, he was the leading tenor at the Bolshoi until 1956.

Lemeshev's operatic repertoire consisted primarily of Russian works along with a particularly significant number of French and a few Italian and German pieces. Almost all works were performed in the Russian language. Unfortunately, very few complete recordings are available, with only excerpts available in spite of Lemeshev's numerous performances on stage in roles such as the Duke in Rigoletto and Almaviva in The Barber of Seville.

Lemeshev's signature role was as Lensky in Eugene Onegin by Pyotr Ilyich Tchaikovsky, and he performed it more than 500 times from 1927 onwards. He performed it for the last time on his 70th birthday, after suffering three heart attacks and having a lung removed.