April 6 spearheaded the January 25, 2011 uprising that ended the autocratic rule of president Hosni Mubarak. It also opposed Mubarak's Islamist successor Mohamed Morsi as well as the military-installed regime that replaced him.
Amr Ali, the movement's general coordinator, and three colleagues were sentenced to three years in prison and ordered to pay fines of 500 pounds ($65), prosecution officials and lawyers said.
They were found guilty of possessing leaflets calling for the overthrow of the current regime, being part of an illegal organisation, inciting a general strike and causing unrest.
Ali has been in detention since September, while the three others were tried in absentia.
His lawyer, Anas Sayyid, contested the charges saying there was "no evidence" to support them.
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April 6 was outlawed in 2014, based on a complaint that accused it of defaming Egypt and colluding with foreign parties.
Its leader Ahmed Maher was sentenced to three years in prison in December 2013 for violating a law banning all but police-sanctioned protests.
And last December, authorities arrested four other April 6 leaders.
Sherif Arubi, Mohamed Nabil, Ayman Abdel Megid and Mahmud Hesham were arrested at their homes on December 28, less than a month before the fifth anniversary of the revolution.
Since the army toppled Morsi in July 2013, the authorities have cracked down on all opposition.
They adopted a new law in November 2013 outlawing demonstrations that have not been given advance authorisation by the police.
Hundreds of Islamist protesters -- as well as dozens of secular and leftwing demonstrators -- have been jailed under the legislation.