William Tell may no longer be the most famous Swiss person in history ... 'cause Tina Turner says she's renouncing her U.S. citizenship to become a full-fledged citizen of Switzerland.

Turner -- who was born in Nutbush, Tennessee -- has been living in Zurich since the mid-90s ... and according to multiple reports, she's decided to make Switzerland her permanent home.

According to a local Swiss newspaper, officials in Switzerland have already decided to GRANT Turner's request for citizenship ... and now it's only a matter of time before the move becomes official.

We called Turner's rep for comment -- who told us she was still trying to get in touch with Tina to clarify the situation.

Also ... yeah, William Tell was Swiss. The more you know ...