Organised by the Orange Order, up to 25,000 participants from the various loyal orders will walk from Stormont to Belfast City Hall watched by an estimated 60,000 spectators.
More than 130 bands have confirmed their attendance at the event which was due to take place last year but postponed due to the Covid pandemic.
Due to the scale of the parade, Grand Lodge grand secretary Rev Mervyn Gibson has urged spectators to arrive early to secure a prime viewing location along the route.
“This will be easily be twice the size of the annual Twelfth parade in the city, so we are encouraging people to come early and pick their spot because it will be difficult to get parked.
“Plan ahead is our key message for spectators. Pick your spot, come early and enjoy the day.
“It is a four and a half mile route from Stormont to the cenotaph,” he said.
Rev Gibson said 265 buses have been booked to bring participants from all over Northern Ireland, who will be joined by people who are travelling over from England, Scotland and as far away as Canada.
“The interest in the parade has been there for several months, but now the excitement is beginning to grow.
“Now that the Rangers [Europa League final] is out of the way, which sadly went the wrong way, this is something else to look forward to and to celebrate.
“This is a major logistical challenge and we appreciate the help of the police, Translink and independent bus drivers in arranging it all.”
The grand secretary said the recent assembly election and current political turmoil has, in some quarters, created a false impression that unionism has been diminished in some ways.
“It is the centennial parade but people are not naive – a lot of people feel that we need to get out on to the streets and show that we are still here,” Rev Gibson added.
The main event will begin at Stormont with platform proceedings at 12 noon – including speeches, a service of thanksgiving and an act of Remembrance.
There will also be family activities and food stalls in the grounds of the Stormont Estate.
The parade will then commence at 1pm, moving along the Upper Newtownards Road, the Newtownards Road, Bridge End, Ann Street, Victoria Street, High Street, Castle Place and Donegall Place, arriving at the cenotaph around 2.30pm
At around 6pm the Belfast lodges and bands will begin parading back to their own districts.
A Translink spokesperson said: “There will be continuous shuttle bus services arranged by the Grand Orange Lodge of Ireland, operating between Stormont and the bottom of the Newtownards Road approximately every 20 minutes for the NI Centenary Parade on Saturday, 28 May.
“Extra capacity will be provided on our trains, with more six car trains in service. Additional relief services will also operate, subject to demand.
“Due to road closures and traffic restrictions in Belfast city centre on Saturday, 28 May, all bus services, Metro, Glider and Ulsterbus will be subject to diversions and delays.