The youngster starred last season despite suffering relegation with Leganes and is set to step into Ever Banega's shoes in the Sevilla midfield.
Sevilla have won the race for the highly coveted Oscar Rodriguez, who arrives from Real Madrid on a five-year deal.
Oscar, 22, will reportedly cost Sevilla €16 million for 75 per cent of his ownership rights, with Madrid retaining the remaining 25 per cent.
"Real Madrid C. F. and Sevilla F. C. have agreed the transfer of Oscar Rodríguez," the Merengue signalled in a statement released on the club's official website.
"Real Madrid would like to thank Oscar for his dedication, professionalism and exemplary conduct throughout the time he has been at our club and wishes him the best of luck in this new chapter."
The gifted midfielder came through Madrid's academy but had spent the two previous seasons on loan with Leganes in LaLiga, helping them to preserve their top-flight status in 2018-19.
Leganes were unable to repeat the feat in 2019-20 as they were relegated on the final day of the season, but Oscar still managed to enjoy a fine campaign individually.
His haul of nine goals made him Leganes' top-scorer and he also supplied a pair of assists.
A fine technician and dead-ball specialist, Oscar's arrival will help alleviate the loss of Ever Banega.
Experienced Argentine playmaker Banega joined Saudi Arabia's Al-Shabab after helping Sevilla to a sixth Europa League crown against Inter.
Oscar had been strongly linked with several other clubs, particularly Milan, but he moves to the Ramon Sanchez Pizjuan where he will get a taste of Champions League football.
The transfer caps a special couple of weeks for the midfielder, who received his first call-up to Spain's senior side on August 20.
It is reported that, as part of the deal, Sevilla will keep Madrid informed of any bids they receive for highly rated centre-back Jules Kounde.