The event linked thousands of members of the People's Mujahedin Organisation of Iran (MEK/PMOI) at their camp in Albania with supporters across the world online including Western politicians, such as former US secretary of state Mike Pompeo, as well as protests in Berlin, London and Brussels.
The MEK, whose political wing is the National Council of Resistance of Iran (NCRI), is proscribed by Tehran and seeks the "overthrow" of Iran's clerical leadership. It accuses Raisi of being responsible for the mass executions of thousands of its members in 1988.
"The mullahs' regime is at an impasse... the Iranian people are nearing victory and will liberate Iran," the NCRI's president Maryam Rajavi told the event from its Ashraf 3 camp in Albania.
She denounced the June election won in a landslide by the hardline Raisi -- formerly judiciary chief -- as a "sham" and predicted his victory would haunt supreme leader Ayatollah Ali Khamenei.
The elevation of Raisi showed the leadership wanted "to close ranks and preserve power" as threats mount, said Rajavi.
"But they have dug their own grave. They are like a scorpion that stings itself when surrounded by flames.... The expiry date for this religious dictatorship has arrived."
She compared the election of Raisi to the declaration of martial law in 1978 by deposed shah Mohammad Reza Pahlavi "which had an outcome contrary to his expectations" leading to the Islamic revolution.
Raisi, who takes office in early August, is accused by the NCRI and international rights groups of playing a key part in the executions of thousands of opposition prisoners -- mostly suspected members of the MEK.
He is accused of being part of a four-man "Death Committee" that sent convicts to their death without a shred of due process.
Most rights groups and historians say between 4,000 and 5,000 were killed, but the NCRI puts the figure at closer to 30,000.
Last year, seven special UN rapporteurs told the Iranian government that "the situation may amount to crimes against humanity" and urged an international probe if Tehran did not show full accountability.
Rajavi described Raisi, Khamenei and new judiciary chief Gholamhossein Mohseni-Ejei as as a "squad of cannibals" who should face charges of crimes against humanity.
She added Raisi should never be allowed to address the UN in New York due to the events in 1988.
Former US president Donald Trump's secretary of state Pompeo said that Raisi would take on the role of "heir apparent" to Khamenei, adding the new president must be held accountable for the 1988 massacres.
"The regime is at its weakest point in decades," he said in a video address.
"They will keep the show going as long as they can. I am confident the people of Iran will not let it continue. The audience wants the show to come to an end."
Warning Europe not to negotiate with Raisi, he said: "Any dealings with Raisi would be tantamount to dealing with a mass murderer."
The MEK backed Ayatollah Ruhollah Khomeini in the 1979 revolution that ousted the shah but rapidly fell out with the new Islamic authorities and embarked on a campaign to overthrow the regime.
The MEK then sided with Iraq under Saddam Hussein in the 1980-1988 Iran-Iraq war.
Its fighters based in Iraq had by 2016 relocated elsewhere in an accord with the US and UN, notably to Albania.
