The 79-year-old former Angolan leader died at the Teknon clinic in Barcelona, Spain, where he was being treated following a prolonged illness, according to the statement.
His successor, Angola's current President Joao Lourenco, declared five days of national mourning and described dos Santos as "unique figure of the Angolan homeland, to which he dedicated himself from a very early age."
One of Africa's longest serving leaders, dos Santos stepped down five years ago.
He frequently described himself as an accidental president, taking the reins after Angola's first leader, Agostinho Neto, died during cancer surgery in 1979.
His rule was marked by a civil war lasting nearly three decades against U.S.-backed UNITA rebels - which he won in 2002 - and a subsequent oil-fueled boom.
He was replaced in 2017 by Lourenco, who despite being from the incumbent's People's Movement for the Liberation of Angola (MPLA), swiftly moved to investigate allegations of multi-billion dollar corruption during the dos Santos era.
Dos Santos had been receiving medical treatment since 2019.
Portuguese news agency Lusa reported last month that the former president was admitted to an intensive care unit in Barcelona.