The Duke of Sussex will attend Saturday's Rugby World Cup final between England and South Africa in Yokohama, Buckingham Palace has said.
Prince Harry, who recently returned from a visit to southern Africa, is patron of the Rugby Football Union.
He watched England win the 2003 World Cup in Sydney and presented the trophy to New Zealand captain Richie McCaw at the last final at Twickenham in 2015.
His brother the Duke of Cambridge is a patron of the Welsh Rugby Union.
Wales missed out on a first World Cup final appearance with an agonising 19-16 semi-final defeat by South Africa.
England qualified for their first final since 2007 with an emphatic 19-7 win over defending champions New Zealand.