An Egyptian court on Saturday ordered the dissolution of the Freedom and Justice Party (FJP), the political wing of the already banned Muslim Brotherhood movement.
The decision follows the designation of the Brotherhood as a "terrorist organisation" in December, after the military overthrew Islamist president Mohamed Morsi.
The FJP came out on top in every election in Egypt between its creation in the wake of the country's Arab Spring uprising in 2011 and Morsi's removal in July 2013.
The Supreme Administrative Court, in its ruling on Saturday, ordered "the dissolution of the Freedom and Justice Party because it broke the law regarding political parties".
"The party and the Muslim Brotherhood are the same thing" and "its members have committed deeds of violence and acts or terror against the nation," state news agency MENA quoted the prosecution case as stating.
According to media reports, the decision is final and not open to appeal.
The party's legal counsel denounced the ruling as "an episode in the series of the counter revolution," in a statement posed on the party's website.
The military toppled Morsi, Egypt's first democratically elected president, after massive protests calling for his removal following a single year of turbulent rule.
Since then, a crackdown by the military-installed authorities on his supporters has killed 1,400 people in street clashes, and some 16,000 Islamists and protesters have been jailed.
At least 200 people have been sentenced to death in speedy mass trials, including Brotherhood leader Mohamed Badie, although none of the sentences has been carried out so far.
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The United Nations has condemned the crackdown as "unprecedented in the recent history" of the world.
Morsi himself is on trial on various charges, and the army chief who ousted him, Abdel Fattah al-Sisi, replaced him after winning a presidential election in May.
Sisi promised in his election campaign to wipe out the Muslim Brotherhood, a process that was already well underway by that time.
The retired general won the contest with 96.9 percent of the vote after having sidelined all major opposition, not just the Islamists but also the youth movements which led the 2011 uprising against dictator Hosni Mubarak.
Morsi's style of government was certainly very different to Mubarak's but many Egyptians quickly lost confidence in the new leader, accusing him of seeking to forcibly impose Islamist rules on the political system and society as a whole.
Morsi also sparked ire for failing to restore the economy, which had nosedived after Mubarak's exit, with investment and tourist revenues tumbling.
Sisi has said his priority is to return Egypt to stability and help recover the shattered economy rather than encourage democratic reforms.
He has ruled the country with an iron rod, frequently vowing to wipe the Brotherhood from the political map.
The December declaration of the Brotherhood as a "terrorist organisation" came amid a slew of attacks on police and military targets claimed by jihadist movements with allegiance to Al-Qaeda.
Then in April, a court barred Freedom and Justice or anyone linked to the Brotherhood from standing in national and local elections scheduled for the autumn.