Connections announced last week that following a glittering career, the John and Thady Gosden-trained eight-year-old was being retired to commence stallion duties from next year.
Racegoers will get their chance to show their appreciation on Saturday week, with Stradivarius being paraded after the Qipco British Champions Sprint.
The son of Sea The Stars won the Long Distance Cup on Champions Day in 2018 and retires with a record 16 Qipco British Champions Series wins. The brilliant Frankel is next best with nine.
Nielsen said: "He has been a joy to own. He turned up and ran his race every time with marvellous consistency.
"The last six years have been an absolute privilege and I particularly want to thank Ascot, Goodwood and York racecourses as well as everyone who has come out to support him during his career.
"He has been an absolute credit to the Gosdens and their staff at Clarehaven who managed to maintain his performance and enthusiasm for so long."
Stradivarius will stand at the National Stud from 2023. Anna Kerr, the National Stud's chief executive, said: "We are delighted to have a racehorse of the calibre of Stradivarius joining the roster at the National Stud.
"He has consistently demonstrated many of the attributes of his sire Sea The Stars - consistency, soundness and a phenomenal temperament. Parading at Qipco British Champions Day provides the perfect opportunity for racing fans to say farewell to a true icon of our sport."