Prince Harry has refused to sign a pre-nup ahead of his marriage to US actress Meghan Markle, it has been reported.

The 33-year-old, who has an estimated $54 million fortune, is determined that his marriage will last and won't need the safeguard.

A friend told The Daily Mail: "There was never any question in Harry's mind that he would sign a pre-nup.

"He's determined that his marriage will be a lasting one, so there's no need for him to sign anything."

The romantic prince follows in his brother's footsteps, with Prince William also refusing to sign a pre-nup before marrying Kate Middleton.

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Prince Harry and Markle at Cardiff Castle in Wales, England. (Reuters)

Prince Harry and Meghan will tie the knot at Windsor castle in May this year, with the US actress becoming Her Royal Highness Princess Henry of Wales.

Harry inherited $18 million after the death of his mother, Princess Diana, and is also reported to have another $36 million in assets.

Meanwhile, Meghan, who was shot to fame for her role in Suits, has a reported fortune of $7 million.

A Buckingham Palace representative declined to comment on the reports.

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Markle and Prince Harry greet fans in Birmingham, England, on International Women's Day. (Reuters)

The loved up couple are in the throes of organizing their wedding, scheduled to take place in May at St George's Chapel at Windsor Castle.

Little detail is known about the big day, but rumours that the Spice Girls and the Foo Fighters could be performing have been circulated.

The Queen this week officially signed off on Harry's wedding to Meghan, giving her formal consent for her "beloved grandson" to tie the knot.

The Royals are inviting members of the public "from every corner of the United Kingdom" to the celebration.

More than 2,600 people will be invited, with 1,200 being members of the public who will have access to the grounds of Windsor Castle on the day.

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Markle and Prince Harry arrive at Westminster Abbey for Markle's first Commonwealth ceremony. (Reuters)

The lucky 1,200 will have an amazing view as the bride and groom arrive and depart the special ceremony.

A statement from Kensington Palace earlier this month read: "Prince Harry" and Ms. Markle would like their wedding day to be shaped to allow members of the public to share in the joy and the fun of the day."

Other guests could include Elton John and former US President Barack Obama.

Charles and Camilla had their televised blessing there in 2005 and it offers the couple a more low key venue than Westminster Abbey, where Kate Middleton and Prince William got married.

St George's Chapel can accommodate 800 guests, whereas the Abbey seats 2,000.

This article originally appeared in The Sun.