Mughniyeh was killed in a car bomb in the Syrian capital Damascus last year
Lebanon's Hezbollah movement has held a mass rally in southern Beirut to mark the anniversary of the assassination of top military commander Imad Mughniyeh.
Mughniyeh is believed to be behind a wave of deadly violence in the 1980s.
The Hezbollah leader, Sheikh Hassan Nasrallah, praised "martyrs" fighting against Israel during a speech broadcast live on a big screen.
The rally comes two days after Lebanon marked the fourth anniversary of the killing of former PM Rafik Hariri.
Mughniyeh is widely believed to have organised the 1983 suicide bombing of the US marine barracks in Lebanon, which killed 241 people, as well as orchestrating the wave of Western hostage-taking in the 1980s.
He had been in hiding for years and was high on US and Israeli wanted lists.
But people who commemorated his death called him a hero, says the BBC's Natalia Antelava in Beirut.
"I want to be like him when I grow up," 13-year-old Mohammed shouted over loud and upbeat music as he sat down besides his friends in a huge building called Martyr's Hall.
Men and women sat separately but their opinion seemed to be the same, our correspondent says.
Many people said they were proud to have Mughniyeh as a martyr and that they were ready to avenge his killing, our correspondent adds.
Hezbollah accuses Israel of killing him, but Israel says it had nothing to do with the car bomb that killed Hezbollah's senior military commander in Damascus last year.
Crowds cheered and shouted as Sheikh Nasrallah - the leader of Hezbollah appeared on the large screens live via videolink.
Mr Hariri greets supporters of his slain father in Saturday's mass rally
Sheikh Nasrallah - who rarely appears in person because of security reasons - said he would keep the promise of revenge he made to Imad Mughniyeh.
He referred to what he said was Hezbollah's right to own and use any kind of weapons, an apparent response to Israeli concerns that Hezbollah may have acquired advanced anti-aircraft missiles that could be used against Israeli planes.
"Why do they (the Israelis) fear us owning such weapons? Because the resistance has the will and the courage to use them," he said.
The Hezbollah leader also commented, for the first time, on the Israeli election, saying that Israel remained an enemy regardless of who was in charge.
In June, Lebanon will vote in a crucial parliamentary election which, our correspondent says, could weaken the country's pro-Western political coalition that currently runs the government, and give Hezbollah much more power.
The Hezbollah gathering came only two days after hundreds of thousands of supporters of the ruling coalition marked the anniversary of the killing of Rafik Hariri, Lebanon's former prime minister.
While addressing the crowd, Saad Hariri, the late prime minister's son and political heir, called on his supporters to take the "fateful election" seriously.