As many as 200,000 people gathered for the memorial service to pay their last respects to the late conservative activist, who was assassinated at a public debate in Utah on 10 September.
"Today, America is a nation in grief, a nation in shock and a nation in mourning," US President Donald Trump said at Charlie Kirk's public memorial in Arizona on Sunday.
Trump, who entered the stage to fireworks and accompanied by Lee Greenwood's live rendition of God Bless the USA, said Kirk was "heinously murdered by a radicalised cold-blooded monster."
"He was assassinated because he lived bravely, lived boldly and argued brilliantly without apology," Trump said to the crowd of thousands gathered at State Farm Stadium in Glendale.
"For millions of Americans ... it's agonising to say goodbye to a patriot who had so much to give."
One of the US' most prominent conservative activists, Kirk was fatally shot at a campaign event at a Utah university on 10 September as he debated members of the crowd.
In his keynote speech on Sunday, Trump said it was Kirk who introduced him to now-Vice President JD Vance as his potential running mate, and frequently asked the US president to speak at his events. "He worked so hard, I didn't want to let him down; he made me feel guilty," Trump recalled.
"To kill a man like this, he doesn't deserve this ... this was a horrible attack on United States of America."
"But the assassin failed at his quest, because his message is bigger and better and stronger than before," Trump exclaimed. "Just think about it, he's bigger today than he was two weeks ago."
"He's eternal, and I just want to say we love him," the US president stated. "That's why I will soon award Charlie with the Presidential Medal of Freedom, it's the highest civilian honour."
On a side note, stating Kirk was a big supporter of "Make America Healthy Again," an initiative by the US Health Secretary Robert F Kennedy Jr, Trump said he is to unveil a major "medical" decision related to autism in children on Monday.
Trump also pledged to "save Chicago" — where Kirk grew up — "from horrible crime," which Trump said was the last thing Kirk told him, explaining Kirk spent much of his youth there and throughout the US devoting himself to "inspiring people to conservative cause."
He pledged to do the same in Memphis and "some others," comparing them to "very safe" Washington, where Trump deployed the US National Guard earlier this year.
Trump concluded his speech by praising Kirk as a "martyr for our freedom" and "our greatest evangelist for American liberty".
"None of us will ever forget Charlie Kirk, and neither now will history," he said.
Trump, who has credited Kirk for playing a pivotal role in his 2024 election victory, was one of many notable speakers and prominent members of his “Make America Great Again” or MAGA movement present at the event, including Vance, Kennedy Jr and Defense Secretary Pete Hegseth.
"God bless all of you for coming here from all over the world to honour and celebrate my Charlie," Kirk's widow Erika Kirk, who spoke right before Trump, said to the thousands gathered at the State Farm Stadium in Glendale.
She then recalled Kirk's message at an event two years ago, when he cited a Bible verse to emphasise his role as someone who engaged in debate across the United States, arguing traditional viewpoints.
"When you say, here I am Lord, use me, God will take you up on that, and he did for Charlie," she stated. "Eleven days ago, God accepted that total surrender from my husband and then called him to his side."
In an emotional speech where she recollected seeing her husband's dead body, Erika Kirk then said she forgave Charlie Kirk's shooter.
"I forgive him because of what Christ did and it is what Charlie would do. The answer to hate is not hate, the answer we know is love and always love. Love for our enemies and love for those who persecute us," she said, vowing to continue the work of Kirk's organisation Turning Point USA as its CEO.
Erika and Charlie Kirk got married in 2021 and have two children.
"I can't help and think they tried to silence my dear friend Charlie Kirk ... and tonight we speak with Charlie and for Charlie louder than ever," Vance said in his speech's opening line, after appearing to a massive applause and cheers of "USA, USA".
"Charlie Kirk built a movement ... and in doing so he changed the course of American history."
"He was Athens and Jerusalem, the city of reason and the city of God, in one person," Vance, who is a close friend of Kirk's, emphasised. "Charlie was slain doing what he loved, telling the truth, proclaiming his faith."
"We have watched people slander him, we watched people justify his murder and celebrate his death ... but it is easy to see in these moments only the worst in our fellow man," Vance said, stating he wished he could have called Kirk to speak to him about what he would encourage him to do in response.
"He would tell me to pray for my friends, but also for my enemies. He'd tell me to put on the full armour of God and get back to work."
“My friends, for Charlie, we must remember that he is a hero to the United States of America. And he is a martyr for the Christian faith," the US vice president said.
"You ran a good race my friend, I love you. We got it from here," Vance concluded.
Donald Trump Jr, who was another close friend of Kirk's, opened his speech by stating he was not a person known to shed a tear, and his sense of humour would often get him a call from his father, in a rare moment of laughter at an otherwise sombre event.
"Charlie brought out the best in us," Trump Jr, who took part in his university debate tours and propped up Turning Point, said. He recalled several events where Kirk decided to go on stage despite threats to his life and safety.
"Charlie led the way, and his message was clear then and is clear now: we won't back down. We won't be intimidated ... We'll not be silenced."
"I'd like to think Jesus was standing to welcome ... the courageous martyr, to heaven," Trump Jr explained, recalling Biblical passages. On the day of Kirk's killing, Trump Jr said he thought, "I'm betting Charlie saw the son of God standing tall to welcome him home."
Both Hegseth and US Secretary of State Marco Rubio praised their "dear friend" in their speeches in Arizona on Sunday, with Rubio stating Kirk's killing was “a political assassination but also a death in the family-type event."
"He died the way he lived, speaking the truth," Hegseth said. "And the gates of hell could not prevail against him."
"He was bold, he was brave, he was a hero," he emphasised. "A warrior for country, a warrior for Christ, he won the race, he finished the fight. Now it's our turn."
"He started Turning Point USA, but this moment is the turning point for the US," Hegseth said. "Charlie, we'll take it from here. God bless."
White House Deputy Chief of Staff Stephen Miller said in his turn at the stage that "the light will defeat the dark". "We will devote the rest of our lives to finishing the causes to which Charlie gave his last measure of devotion," Miller said in a religious-themed message.
The first to speak on Sunday was Rob McCoy, the pastor emeritus of Godspeak Calvary Chapel in California, who said he was Kirk's pastor of choice.
“Charlie was never afraid, because he knew his life was secure in the hands of God,” McCoy, who is a vocal supporter of Trump, said.
Florida Representative Anna Paulina Luna called on the youth to carry on Kirk's legacy, stating he became “one of the most powerful men in the world.”
“Charlie poured out his youth, his energy and his unshakable resolve ... to mobilise millions this past election cycle to reclaim the principles of truth and self-governance that define our exceptional nation,” Luna said.
Conservative activist Jack Posobiec slammed the left in his speech, stating Kirk's movement must continue.
“We will never, ever let the left, the media or the Democrats forget the name of Charlie Kirk,” Posobiec said, finishing with a pledge to end the “evil disease … that took Charlie from us.”
Kirk's alleged shooter Tyler Robinson, who hails from a Republican Utahn family, "had started to lean more to the left,” according to a testimony by Robinson's mother, officials said. No links to any left-wing groups and Robinson have been found so far, according to reports.
The memorial service for Kirk drew as many as 200,000 mourners on Sunday, according to reports. Members of the public began lining up outside the stadium before dawn, and the 63,400-seat stadium — which can expand to a total of 73,000 for mega-events — quickly filled with people dressed in red, white and blue, organisers said.
Tesla CEO Elon Musk, once a close ally of Trump, had also been spotted in the crowd, and the two shared a handshake.