The Muslim Brotherhood's Freedom and Justice party elected on Friday Saad al-Katatni as its new leader, succeeding Mohammed Morsi who resigned from the post after becoming Egypt's president in June, DPA reported.
Al-Katatni, who is seen as a political pragmatist, was the speaker of the first parliament elected after the ouster of president Hosny Mubarak last year. The Islamist-dominated parliament was dissolved in June.
The university professor and former secretary-general of the party beat rival Essam al-Erian with 67 per cent of the vote.
The party's internal elections came as thousands of people rallied against an assembly drafting Egypt's new constitution, condemning it as being dominated by Islamists.
Protesters marched across Cairo until they gathered in Tahrir Square, where some 200 people were injured in clashes between Islamist and anti-Islamist protesters last week.