Frenchman Nianzou, 20, who joined Bayern from Paris Saint-Germain in the summer of 2020 on a free transfer, has largely been a peripheral player in the Bavarian capital.
German newspaper Bild reported Bayern will receive a fee of 16 million euros ($16.3 million), which could rise to 20 million euros with bonuses.
Nianzou has made 28 appearances in two seasons in Munich, the vast majority of which have come from the bench as the France under-20 captain has struggled with injuries and Covid-19.
Despite scoring his first goal towards the end of Bayern’s 2021-22 campaign against Union Berlin, Nianzou’s hopes of regular first-team action in Munich were low.
In addition to the arrival of central defender Matthijs de Ligt in July and countryman Dayot Upamecano in the summer of 2021, Lucas Hernandez is also ahead of Nianzou in the pecking order.
Sevilla had been on the lookout for a new centre-back since the departure of Jules Kounde to Barcelona.