The online fashion retailer will relaunch the department store as an online-only operation from next year.
The sale was confirmed to the London stock exchange on Monday morning.
It comes just days after Debenhams administrators FRP Advisory said they were still in talks with “a number of third parties regarding the sale of all or parts of the business”.
Boohoo said it was a “transformational deal” and a “huge step”.
The company highlighted how Debenhams has six million beauty shoppers and 1.4 million Beauty Club members.
It said: “The group intends to rebuild and relaunch the Debenhams platform, helping further the group’s stated ambition to lead the fashion eCommerce market, and grow into new categories including beauty, sport and homeware.”
In hints that it intends to take on the might of Amazon, Boohoo said it would create the UK’s largest marketplace across fashion, beauty, sport and homeware – expanding the range of products sold via Debenhams marketplace by maintaining current third party relationships and expanding further.
Debenhams’ own fashion brands will also be absorbed into Boohoo’s current portfolio and sold via the Debenhams website.
Boohoo chief executive John Lyttle said: “The acquisition of the Debenhams brand is an important development for the group, as we seek to capture incremental growth opportunities arising from the accelerating shift to online retail.”
Founder and executive chairman, Mahmud Kamani, added: “Our acquisition of the Debenhams brand is strategically significant as it represents a huge step which accelerates our ambition to be a leader, not just in fashion eCommerce, but in new categories including beauty, sport and homeware.”
Boohoo has already snapped up a number of High Street brands out of administration. It bought up Oasis, Coast and Karen Millen, but not the associated stores.
Boohoo said Debenhams was expected to relaunch on Boohoo's web platform in early 2022.
Debenhams had already announced significant job losses and the permanent closure of six stores, including its flagship outlet on London’s Oxford Street.