Michelle Bachelet, 62, has been sworn in as the president of Chile, her second time in office.
The socialist leader was inaugurated in a ceremony in the city of Valparaiso after her election win in December over conservative rival Evelyn Matthei.
Outgoing conservative President Sebastian Pinera wished his successor good luck.
Ms Bachelet is the first Chilean president in over half a century to return for a second term.
In a ceremony attended by leaders from the region, including Argentina's Cristina Fernandez de Kirchner, Ecuadorean leader Rafael Correa, Peruvian president Ollanta Humala and Bolivia's Evo Morales, Ms Bachelet swore the oath of office.
President of the Senate Isabel Allende placed the presidential sash around Ms Bachelet's neck - the first time it was passed from one woman to another in Chile's history.
Ms Bachelet won 62% of the vote in the second round of the presidential election in December, well ahead of the 38% cast for Evelyn Matthei.
She campaigned on a promise to spend $15bn (£9.2bn) on reforming education, improving health care and reducing income disparity.
She also wants to increase taxes to offer free university education and reform political and economic structures dating from the 1973-1990 dictatorship of Gen Pinochet.
Chile is one of the richest countries in Latin America, but tens of thousands have staged protests over the past few years to push for a wider distribution of wealth and better education.
Analysts say Ms Bachelet's ambitious plans for reform may prove hard to finance, especially as the growth of Chile's economy has slowed.
Ms Bachelet already served one term as president from 2006 to 2010.
Under Chile's constitution she was banned from running for a second consecutive term, even though her popularity ratings remained high.