Harald, a reformer who spent more than three decades on the throne after gradually emerging from the shadow of his popular and charismatic father, died at a time of multiple crises for the Norwegian royal family.
A procession on foot from the royal palace to Oslo Cathedral will start at midday on Wednesday (8pm AEST), followed by a church ceremony which will begin with a nationwide minute of silence.
Among the guests expected are Britain's Prince William and Princess Anne; Japan's Crown Prince Akishino and Crown Princess Kiko; Spain's King Felipe, Queen Letizia and Queen Sofia; Sweden's royal family; and Denmark's King Frederik and Queen Mary.
Queen Mette-Marit, 53, is expected to attend but will travel by car with Harald's widow, Queen Sonja, 89, as she recovers from a lung transplant undertaken in June.
Mette-Marit was forced to cancel plans last week to attend her husband King Haakon VIII's oath ceremony in parliament due to complications following her operation.
Her son, Marius Borg Hoiby, from a relationship before her marriage to Haakon, is also expected at the funeral despite being under house arrest and wearing an ankle monitor after his conviction for rape and domestic violence. He is appealing the sentence.
Hoiby was one of the pall-bearers during the transfer of Harald's coffin to the royal chapel, drawing criticism in some quarters.
After the service, a smaller procession will accompany the coffin to the royal crypt at Akershus Fortress overlooking Oslo harbour. There, Harald's coffin will be placed in a sarcophagus, alongside those of his parents.
When Haakon emerges from the crypt, the national mourning period will formally end and flags that have flown at half-mast since Harald's death will be raised again.
Norwegian police said securing the funeral is the largest planned operation in the force's history, with large crowds expected in central Oslo. School children will be allowed to skip classes to attend the funeral.
Hundreds of thousands of Norwegians have paid tribute to Harald by leaving flowers, candles and flags outside the Royal Palace or filing past his coffin in the royal chapel.
Many mourners have praised Harald's warmth and inclusiveness, while Haakon described him as a wonderful father in his first address to the nation as sovereign.