Mubarak, 88, left the Maadi Military Hospital where he had been detained for the past few years, heading to his home in Heliopolis, his lawyer Farid El-Deeb told local media.
Earlier this month, the Appeals Court gave its final verdict and acquitted Mubarak over charges of taking part in killing protesters during the 2011 revolution that toppled him.
Mubarak was sentenced to life in prison in 2012 for taking part in killing over 200 protesters during the 18-day revolt which began on January 25, 2011, but a retrial was ordered on appeal.
In 2013, the court cleared Mubarak and his seven aides, including his interior minister Habib el-Adli, from the charge, but public prosecutors appealed the sentence.
Mubarak will face retrial in the "Ahram's gift" case as he and some of his aides are accused of accepting gifts from the state-owned Al-Ahram newspaper.
Mubarak, who ruled Egypt since the 1952 abolition of the monarchy, became president in 1981 after Anwar Sadat's assassination.
He was initially arrested in April 2011, two months after leaving office and had been at the hospital since 2013, when he was transferred there on bail from Torah prison.
A judge at a trial in May 2015 decreed that Mubarak could be released from detention.
However, the government of President Abdul Fattah al-Sisi was reportedly reluctant to free him, fearing public backlash that may accompany such a move.
Sisi served as Mubarak's military intelligence chief and led the military's overthrow of his democratically elected successor Mohammed Morsi in 2013.
Hundreds of people are believed to have been killed as security forces clashed with protesters in Cairo, Alexandria, Suez and other cities around Egypt during the 18-day uprising that forced Mubarak to resign.
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