Mansour (67) was sworn in at the Constitutional Court in a ceremony telecast live on state television.
"I swear to preserve the system of the republic, and respect the constitution and law, and guard the people's interests," Mansour said as he took the oath of office.
Egypt's chief justice Adly Mansour delivers a speech during his swearing-in ceremony as the country's interim president in the Supreme Constitutional Court (Pic-AFP)
Mansour, as per a decree by army chief Gen Abdel Fattah Sisi, will serve as the Arab nation's interim president until a new leader is elected.
Last night, the army ousted Morsi, who took office a year ago as the country's first democratically elected president after days of mass rallies across the country demanding removal of the Islamist leader belonging to the Muslim Brotherhood.