Bagpipe players begin the ceremony with "Amazing grace", followed by the artist Chris Tomlin and the Christian ballad "Holy forever". After the American national anthem, a long series of speakers followed, including Kirk's pastor, teachers and colleagues.
Right-wing debater Charlie Kirk was co-founder of the conservative organization Turning Point USA. He was shot dead on September 10 when he spoke at Utah Valley University in the USA.
"Became a martyr"
The memorial service for Kirk - whom Donald Trump attributes a crucial role in his election victory in 2024 - is being held at the sports arena State Farm Stadium in Glendale, home ground for the NFL team Arizona Cardinals, with strict security measures similar to those at the Super Bowl. Tens of thousands of people began queuing early in the morning.
My friend became a martyr because he used his voice in peaceful dialogue, says Michael McCoy, who was Charlie Kirk's chief of staff, during the ceremony.
The murder of Kirk has sparked debate about political violence and freedom of speech at a time of deep political division.
Today we will celebrate a great man's life, Trump said to reporters when he left the White House on Sunday morning on his way to Arizona for the ceremony.
It will be a tough day.
Also speaking at the memorial service are Vice President JD Vance, Defense Minister Pete Hegseth, Intelligence Chief Tulsi Gabbard and other prominent right-wing politicians.
"The movement will not die"
The murder of Kirk has raised concerns among some Americans that Trump is trying to exploit the murder to silence critics. Trump has accused the "radical left" of Kirk's death. Several people have lost their jobs after making comments about Kirk that are considered offensive. ABC also paused Jimmy Kimmel's talk show after criticism from Trump supporters and the head of the US Communications Authority (FCC).
Kirk's widow Erika Kirk, who now leads Turning Point, held an emotional speech where she promised that "the movement my husband built will not die."
22-year-old Tyler Robinson from Utah is being held in custody suspected of Kirk's murder and risks the death penalty if convicted. His motive is still unclear.
