Andrés Manuel López Obrador – Mexico’s first leftist president in seven decades – has been sworn in at a ceremony in the country’s parliament.
The former Mexico City mayor pledged on Saturday to end corruption and impunity to transform the nation on behalf of the poor and marginalised.
The 65-year-old, popularly known by his initials Amlo, won a landslide victory in July – his third presidential bid.
The political veteran begins his six-year term with approval ratings of 56%.
His predecessor Enrique Peña Nieto leaves office with only 24% – his administration was plagued with corruption scandals and murder rates reaching record-high levels.
President López Obrador inherits an immediate foreign policy issue – what to do about the thousands of Central American migrants camping on the US-Mexico border.
Foreign dignitaries including US Vice-President Mike Pence, first daughter Ivanka Trump and Venezuelan President Nicolás Maduro attended the inauguration in the capital.
British Labour leader Jeremy Corbyn, who Mr López Obrador considers a close friend, was also present.
Mr López Obrador – whose leftist National Regeneration Movement party (Morena) will lead a coalition government – later took part in a traditional indigenous ceremony in Mexico City’s Zocalo square.