Alexey Sayapin was born in Saratov in 1985 and began studying singing at the local conservatory in 2003. In 2008 he completed his studies with honors and initially sang important roles in his field in Russia, including Edgardo in "Lucia di Lammermoor" at the Saratov Opera and Alfredo in "La traviata" at the Mikhailovsky Theater in St. Petersburg. In 2007 he was a prizewinner at the Elena Obratsova Competition in St. Petersburg, in 2008 at the Galina Vishnevskaya Competition in Moscow and in the same year he won first prize at the Luciano Pavarotti International Tenor Competition in Moscow. The young tenor was invited by Plácido Domingo to the Operalia competition, where he also won an award. In the 2010/11 season, Sayapin was a member of the Young Artist's Program at the Los Angeles Opera for two years, where he made his debut as Tybalt in "Roméo et Juliette" (Gounod). At the 2011 Aspen Festival he made his debut as Lysander in Britten's "A Midsummer Night's Dream". In the 2012/13 season he sang Pinkerton in "Madama Butterfly" at the Santa Barbara Opera and made his German debut with Verdi's "Messa da Requiem" as part of concerts for Holocaust Remembrance Day.
From 2013 to 2016 the artist was a permanent member of the Aalto Theater Essen. At this house he was successful as Arturo alongside Marlis Petersen (La Straniera) as well as Stewa (Jenufa), Macduff (Macbeth), Prinz (Amour des trois oranges) and Alfredo (La Traviata).
Alexey Sayapin was seen at the Theater Aachen in the 2018/19 season as Roméo (Roméo et Juliette), Izmailov (Lady Macbeth of Mtsensk) and Alfredo (La Traviata).
In recent years he has appeared at the Aachen Theater in roles such as Roberto (Maria Stuarda), Macduff (Macbeth) and Luici and Rinuccio in Puccini's Trittico. In 2017 he sang concert performances of Pique Dame and Les Noces with the Lucerne Symphony Orchestra.

In the 2020/21 season, Alexey made his debut in the role of Andrey in Tchaikovsky's "Mazeppa" at the Cottbus State Theater.

He has been part of the Cottbus State Theater ensemble since the 2021/22 season.