"Because of his charisma, his leadership and his political experience", the ruling party unanimously chose Obiang as its candidate for the November 20 poll, Vice President Teodoro Nguema Obiang Mangue -- who is also Obiang's son -- wrote on Twitter.
President Obiang, 80, is the longest ruling head of state in the world excluding monarchs.
His Democratic Party of Equatorial Guinea (PDGE) holds 99 of the 100 seats in the outgoing lower house of parliament and all 70 of the senate seats.
But it had not been clear who would be named as the party's candidate in the presidential ballot.
At one point, Obiang's wealthy jet-setter son Teodoro Nguema Obiang Mangue, nicknamed "Teodorin", seemed to have been lined up to stand in the elections. In the end, however, he was not chosen as a candidate last year.
The PDGE was the country's single legal political movement until 1991, when multi-party politics were introduced.
But Obiang himself has never officially been re-elected with less than 93 percent of the vote.