Lalao Ravalomanana was picked as the candidate of her husband's political party at a weekend meeting, party officials said Monday.
"It was absolutely a natural consensus between members of the Ravalomanana Movement and [ex)-president Ravalomanana," Mamy Rakotoarivelo, a representative of the party told AFP.
But her nomination may inflame tensions in the troubled Indian Ocean island nation and complicate the holding of elections due on July 24.
Lalao and her husband had been exiled in South Africa since the coup in 2009, but the former first lady was allowed back into the country on March 12 to be with her seriously ill 83-year-old mother.
Madagascar's strongman Andry Rajoelina allowed her to return on condition she would abstain from all political activities.
That demand now appears to have been flouted.
The deadline to submit presidential nomination papers is May 3. Observers suspect Ravalomanana's papers are likely to be rejected on the grounds she has not resided in Madagascar for the last six months.
By the deadline date, she would have just been in Madagascar for slightly over seven weeks. She risks expulsion from the country.
Exile
Ravalomanana, the mother of four, has no known political experience.
She created the food conglomerate Tiko with her husband and became its chief executive before they were forced into exile in 2009.
The couple tried unsuccessfully several times to return to Madagascar, with authorities believing that their return could spark unrest.
Ravalomanana's party said the former head of state hopes to return to Madagascar after the elections.
The main political foes Rajoelina and Marc Ravalomanana have opted to stay out of the 2013 race, saying their absence would favour a smooth transition.
Madagascar has been mired in political crisis since Rajoelina overthrew Ravalomanana's government in March 2009 with the army's support.
The July elections are expected to end the long-running crisis and restore the island to constitutional order.
A week ago Rajoelina's party named Edgar Razafindravahy, the mayor of the capital, as its candidate in the presidential vote. – AFP