The club's administrators Quantuma announced that a deal was finalised for an undisclosed fee.
The news will come as major relief for the supporters who will watch their team compete in the third tier of English football for the first time since 1986.
A statement from the administrators said: "Quantuma joint administrators, Andrew Hosking, Carl Jackson and Andrew Andronikou are delighted to confirm the completion of the sale of the business and assets of Derby County Football Club ("The Club") to Derbyshire based property group, Clowes Developments (UK) Ltd ("Clowes") for an undisclosed amount.
"The transaction sees the Club exit from administration and be brought under the same ownership structure as its stadium, Pride Park."
Quantuma accepted the bid from property developer David Clowes last Sunday, with the deal reaching completion on Friday.
Clowes emerged as favourite for the takeover after American businessman Chris Kirchner withdrew his offer.
The new owner has already pledged to purchase Pride Park and also agreed to issue the club with an interim loan.
Joint administrator Jackson said: "We are very pleased to have achieved today's sale, in a deal which secures the long-term future of the club, and one which represents the very best outcome for creditors.
"I would like to express my sincere thanks to the club's staff players and the fans for their loyalty, and patience, as they supported the club through the administration."
Joint administrator Hosking added: "The level of complexity involved in bringing this matter to a conclusion has been unparalleled and we are grateful to all stakeholders and their advisers, for their hard work which has enabled us to overcome a magnitude of challenges, and allow the rescue of this historic club."
Quantuma were in talks with several other interested parties, including former Derby owner Andy Appleby and sports retail billionaire Mike Ashley, who sold Newcastle United to a Saudi Arabian-back consortium last season.
Derby, whose debts have been reported to be in the region of £60million, were docked a combined 21 points last season - 12 for entering administration and a further nine after admitting they breached EFL financial regulations.