Egypt's Justice Minister Ahmed Mekki resigned on Sunday ahead of a cabinet reshuffle in which he was expected to be replaced, state media reported.
President Mohamed Morsi had said on Saturday he would order the reshuffle "soon," after months of pressure by opposition groups that demand an overhaul of the government before dropping a boycott of parliamentary elections.
Egyptian media had reported that Mekki would be one of the ministers replaced in the shake up, which a presidential aide told AFP would affect up to eight ministries, including "important ones."
The official Al-Ahram newspaper reported on its website that Mekki "officially tendered his resignation to the prime minister."
Mekki could not be reached for comment.
Prime Minister Hisham Qandil may turn down the resignation, as he had done in the past with other ministers.
Once a leading dissident judge under ousted president Hosni Mubarak, Mekki has faced criticism from both the opposition and Morsi's supporters.
He had threatened to resign after Morsi adopted extensive powers in November that infuriated the judiciary, but remained in his post.
Qandil's government, appointed after Morsi's election in June, has tried to cope with a haemorrhaging economy despite billions of dollars in aid from energy-rich Qatar and some other countries.
The opposition has set Qandil's departure as a condition for dropping a boycott of parliamentary elections, possibly in the autumn.