The purchase of Vergemont Station near Longreach will conserve nearly 350,000 hectares, thanks to the $21 million donation from an anonymous philanthropist.
The acquisition by the Queensland government was completed with the support of The Nature Conservancy, to which the donation was made.
The working cattle farm is a habitat for the elusive and endangered night parrot, the vulnerable yellow-footed rock wallaby and threatened Opalton grasswren.
It also sits at the headwaters of the Lake Eyre Basin, one of Queensland's most important inland river catchments.
"Vergemont has a number of ecosystems that are really important," James Fitzsimons from The Nature Conservancy told AAP.
"This purchase is most likely the single largest donation to buy land for conservation in Australian history."
Almost all of the property is covered in remnant vegetation.
The land contains 34 different regional ecosystems, ranking it higher than most of the existing national parks in terms of regional ecosystem representation.
Sitting adjacent to the recently acquired Tonkoro Station the purchase will create a corridor that conserves almost one and a half million hectares, according to the Queensland government.
"This acquisition will see the total area of land currently protected or acquired for future dedication as protected areas push over 15 million hectares for the first time," Environment Minister Leanne Linard said.
"Dedication of Vergemont Station, and the recently acquired Tonkoro and Melrose Stations, as national park, will also generate a range of economic activity in the local region."
The government said boulder opal mining operations will be allowed to continue on 40,000 hectares of the property, but the rest of it will be converted into a national park.
