15,000 apprentice accompanied by 140 bands marching through Derry City Centre this afternoon.
Today's parade marks the 322nd anniversary of the ending of the Siege of Derry in 1689.
Before the main demonstration at lunchtime, a number of local Apprentice Boys are walking the city's walls before a religious service in St Columb's Cathedral and a reanactment of the relief of the city. The pageant is the culmination of the Maiden City Festival, which has been taking place all week.
Dissident republicans are protesting, but Apprentice Boys' governer Jim Brownlee is hopeful the protests will not disrupt the day.
He told the BBC the Apprentice Boys respect their right to protest, and hope those protests are peaceful, and the parade and the protests, can pass off peacefully.