Europe's oldest reigning monarch Harald, 89, died peacefully at 6.35am on Friday at Oslo University Hospital, according to the Royal Court.
His son, who had kept vigil at his bedside along with other family members, inherited the throne and will be known as Haakon VIII, the Royal Court said, while his wife Mette-Marit is to be queen.
His oldest child becomes Crown Princess Ingrid Alexandra and the heir to the throne.
Thousands of people accompanied the late king on his final journey to the Royal Palace in the evening.
His coffin was transported in a funeral procession consisting of several vehicles from the hospital towards the palace in the centre of the Norwegian capital.
Despite the pouring rain, the streets along Harald's route were lined with people bidding him farewell, some holding umbrellas and others waving Norwegian flags.
Haakon VIII, Queen Mette-Marit and other close relatives of the late head of state followed the hearse in other vehicles.
The coffin containing Harald's body is to be laid in state later in the palace chapel.
Members of the public will then be able to pay their respects to their long-serving monarch until the funeral.
Haakon VIII will take his oath of allegiance to the constitution at 1pm on Tuesday.
The date was announced to the broadcaster NRK on Friday by the Speaker of the Norwegian parliament Masud Gharahkhani.
The oath is mandatory for the new monarch and will take place in the parliament, known as the Storting, close to the palace.
The new king will also deliver a short address, which will be televised.
According to the parliament, the address will emphasise that the monarch's power is limited and regulated by the constitution.
Norway no longer stages a traditional coronation.
Harald's father Olav V introduced a new blessing ceremony in 1958, which Harald and his wife Queen Sonja continued in 1991.
A similar ceremony is expected this time.
The blessing is traditionally followed by a tour of Norway.
According to an unconfirmed media report, Haakon is set to deliver his first speech as king on Saturday.
So far, the royal house has merely stated that Haakon will deliver a live-broadcast speech to the Norwegian people "in the early days" of his reign.
Harald had been in hospital since the beginning of last week, receiving treatment for haemolytic anaemia, which had led to fluid retention in his body.
He subsequently contracted a bacterial infection of the bloodstream.
The Norwegian king had long been in poor health.
Since 2024, he had been permanently dependent on a pacemaker.
He also frequently suffered from respiratory illnesses.
In February, the monarch was taken to hospital with an infection while on holiday in Tenerife with his wife.
Walking also became difficult for him in recent times.
Despite this, Harald had ruled out stepping down from the throne early in favour of Haakon.
He carried out his royal duties until the very end.
Norwegians valued King Harald V for his reserved manner.
