The forces said in a statement that the property was located at one of the approaches to the Muskö Naval Base. Swedish media have reported that it belongs to a Russian businessman with ties to the Kremlin.
The military said the location "has unique conditions for strengthening the defence of Muskö Naval Base, particularly against drones", and was currently owned by an individual with Russian citizenship.
"The development of Russian drone warfare has changed the threat landscape for Sweden," the Swedish Armed Forces said.
"There is therefore a need to take measures to protect Sweden against the threat posed by both aerial and sea-going drones," it added.
It said the property was "the only location" that was not at their disposal "in order to establish an effective defence" of the base, "particularly against drones".
The Swedish Fortifications Agency – which manages defence-related properties – had therefore requested, on behalf of the Armed Forces, that the government take over ownership.
Newspaper Expressen reported that the property belonged to Russian businessman Stanislav Aleshchenko – who has links to Russian President Vladimir Putin – although the property was formally in his wife's name.
Swedish media had previously reported that he was building a massive holiday home and that the government had looked into ways to stop the construction.
Public broadcaster SVT reported that the property has been "a thorn in the Armed Forces' side".
"We are facing the most serious security situation since the end of the Second World War, and the threat against Sweden and the Alliance is real," Chief of the Defence Staff Carl-Johan Edström was quoted as saying in the Armed Forces statement.
Sweden ended two centuries of military non-alignment and joined Nato in 2024 after Russia's 2022 invasion of Ukraine.