European Union Foreign Policy Chief Catherine Ashton arrived in Cairo late on Tuesday, in a visit to promote reconciliation between Egypt's interim administration and the Muslim Brotherhood, Al-Ahram Arabic news website reported.
On previous visits, Ashton and other Western envoys tried unsuccessfully to push for an "inclusive" process to end the stalemate following the removal of Islamist president Mohamed Morsi, and urged Egyptian authorities not to use force against his supporters.
During her three-day visit, the EU envoy is expected to hold talks with key members of the Egyptian government and army chief Abdel-Fattah El-Sisi, as well as some Brotherhood leaders who are not in custody.
Earlier media reports had said Ashton would delay her visit to Cairo until Wednesday.
Mohamed Morsi's Muslim Brotherhood has been rocked by a sustained clampdown that has seen most of its top leaders arrested. A preliminary court vedict has also banned all the group's activities and ordered its assets seized.
Ashton has visited Egypt 11 times over the past two years. In her last visit in July, the top diplomat was the first foreign envoy to visit Morsi - at an unknown location - since his popularly-backed ouster by the military on 3 July.
The EU strongly condemned a crackdown by security forces on pro-Morsi protest camps in Cairo and Giza on 14 August, which killed hundreds. Ashton has voiced fears at the growing levels of violence and polarisation since Morsi’s ouster.