Born in 1947, Mrs Arroyo is the daughter of Diosdado Macapagal, who led the Philippines during the 1960s.
She was a classmate of former US President Bill Clinton at Georgetown University in Washington, and has a doctorate in economics from the University of the Philippines.
Mrs Arroyo's route into politics was a conventional one. She started her government career with the Department of Trade and Industry, and was elected into the Senate in 1992, and again in 1995.
Three years later she won a landslide victory to become vice-president to Mr Estrada.
Her style could not be more different from that of Mr Estrada, or his friend Fernando Poe Junior, who ran against her in the 2004 presidential election.
Her sometimes cold and businesslike manner has made it difficult for her to win the support of poorer voters.
She tried to address this problem during the run-up to the 2004 presidential campaign by injecting some glamour into her campaign.
She chose as her vice-president Noli De Castro, who got into politics because of his experience as a news anchor.
As is often the norm in the Philippines, Mrs Arroyo's time in office has been dogged by political in-fighting and rumour.
Just months after she took power in place of Mr Estrada, his supporters stormed the gates of the presidential palace demanding she resign.
Mrs Arroyo managed to ride the storm, but in 2003 there was another attempt to unseat her, when more than 300 soldiers seized a Manila hotel and again demanded she step down.
The rebellion was put down peacefully, but both her defence secretary and military intelligence chief resigned in the wake of the incident.
Her victory in the 10 May 2004 election - announced by a congressional committee six weeks later, following a contentious vote-count - again confronted her with tough challenges, notably grinding poverty, a restive military and spiralling debt.
In 2005, a tape recording of a phone call - apparently between Mrs Arroyo and an election commissioner during the previous year's election - looked set to weaken her position.
Mrs Arroyo admitted she had called an election commissioner during the election, but denied trying to influence the vote, as the opposition claimed.
She rode out calls for her to resign, an attempt to impeach her, and allegations her husband, son and son-in-law were involved in influence peddling and bribe taking.
In June 2005, her husband Jose Miguel - widely known as Mike - moved overseas, in a move designed to silence her critics.