The intervention follows an announcement by House of Fraser that it had been forced to appoint administrators after talks with potential investors collapsed.
A statement from Sports Direct said: "Sports Direct International plc announces the acquisition of the business and assets of House of Fraser from the administrators of House of Fraser Limited, House of Fraser (Stores) Limited and James Beattie Limited, the House of Fraser group's main operating companies, for a cash consideration of £90m".
It said it had put questions to House of Fraser earlier this week in relation to its future but has not yet received a response.
House of Fraser in The Oracle. Our deal was conservative, consistent and simple.
This morning's announcement confirms that Sports Direct has acquired all of the United Kingdom stores of House of Fraser, the House of Fraser brand and all of the stock in the business.
House of Fraser's pension scheme was expected to enter assessment by the Pension Protection Fund lifeboat, a spokeswoman for the PPF said.
This precipitated a three-way tussle between retail billionaires Ashley and Philip Day as well as a proposal by Alteri Investors, with Ashley ultimately emerging on top.
It is unclear what Mr Ashley's plans are for the chain - but the move could in theory offer a reprieve for staff and customers.
US issues advisory, asks its citizens not to visit flood-hit Kerala
Earlier, the United States had issued an advisory, asking its citizens not to visit Kerala because of the flash floods. According to the government reports, more than 10, 000 has been moved to the 157 relief camps across the state.
Why 'Fortnite' bypassing Google Play could be a security nightmare
Fortnite is a mega-popular, fight-the-demons, post-apocalyptic video game, and it's about to come out on Android . Epic will also offer downloads of the game on its website in the coming days for most Android smartphones.
Bitcoin, Ethereum and Ripple - how will they perform in the future?
BCH is seeing a daily loss of around 14.2 percent and is the fourth highest market valuation among every coin in existence. Further price action under this level would see BTC head below $6,000 and towards support at $5,932, the February 6 low.
The deal will see the tycoon tighten his grip over the British high street, adding to his sports retailing and "premium fashion" empire.
Buying other businesses and strategic stakes forms part of that plan - equity investments have been made in Debenhams, French Connection, Game Digital, Findel and Goals Soccer Centres.
Prior to the latest crisis, House of Fraser had recently agreed a so-called Company Voluntary Arrangement (CVA) with landlords to close half of stores, with 6,000 jobs in the firing line.
Sports Direct wrote to HoF's management last month to set out the terms of a rescue deal, saying it was willing to structure a transaction on similar terms (subject to due diligence to confirm the level of investment/cash injection required) to one proposed by the Chinese owner of Hamleys.
Richard Lim, of Retail Economics, said: "The combination of rapidly rising costs against a backdrop of seismic shifts in the way we all shop is pushing traditional business models to the brink".
"Nevertheless, this is a part of the industry that is under a huge amount of pressure".
Another first was that it was the retailer's first sustainable and green store.