"They will be making sure it reflects who they are as a couple," a palace spokesperson has previously said, adding that the day will be full of "fun and joy" and will "reflect the characters of the bride and groom".
Read on to see how Harry and Meghan's big day will differ from William and Kate's…
Like most royal couples, Prince William and Kate followed in tradition and married at Westminster Abbey. Because of the smaller scale of their wedding, Harry and Meghanchose St George's Chapel at Windsor Castle, where the Prince was baptised. A palace spokesperson described the castle as a "very special place" for Harry, adding that the couple had spent time there together during their 16-month pre-engagement romance.
The number of guests
Because Prince William will one day be King, his royal wedding to Kate was a huge affair, with around 1,900 guests invited to the religious ceremony at Westminster Abbey. Around 600 people were then invited to a luncheon at Buckingham Palace, hosted by the Queen. William and Kate's closest friends and family members, around 300 people, had the privilege of staying for the evening dinner.
Prince Harry and Meghan's wedding will be a much smaller – but still spectacular – event. Their venue, St George's Chapel, has a maximum capacity of 800 people. After the ceremony, the couple will toast their union at St George's Hall. Prince Charles will then host a private reception for the newlyweds and around 300 of their closest family and friends.
Prince William and Kate used the truly majestic 1902 Imperial State Landau to greet wellwishers after their wedding. The open-top carriage, which was built for King Edward VII, took the newlyweds from Westminster Abbey to Buckingham Palace.
On Harry and Meghan's big day, the couple will also take part in a carriage procession. Members of the public will be able to catch a glimpse of the newlyweds as they are driven from St George's Chapel down Castle Hill, processing along the High Street and through Windsor Town, before returning to Windsor Castle along the Long Walk.
It's not yet known what carriage Harry and Meghan will take, but it will likely be open-topped so that wellwishers can see the couple. The carriage will probably be less grand than William and Kate's, but still regal. They could choose an Ascot Landaus, which is what Prince Harry and Pippa Middleton rode for the 2011 royal wedding in their roles as best man and maid of honour. Or, they could select a Semi-State Landau, which was particularly popular with Queen Victoria.
Their first appearance as newlyweds
One of the most heartwarming moments of the royal wedding was when Prince William and Kate made their first appearance as newlyweds on the balcony of Buckingham Palace.
It was a real pinch-me moment for Kate, who exclaimed "wow" as she took in the thousands of wellwishers standing along The Mall. The couple indulged the crowds in not one but two kisses, as William turned to Kate and said: "Let's give them another one. I love you."
Harry and Meghan will miss out on an iconic balcony kiss, given their choice of venue. It's likely that their first high-profile appearance as man and wife will be on the church steps of St George's Chapel, and it's there that Harry and Meghan may share their first public kiss.
The guest list
William and Kate had a host of famous faces in their congregation, including William's friend David Beckham and his wife Victoria, who was pregnant with their daughter Harper at the time. Sir Elton John, who was good friends with Princess Diana, was also invited, and is also expected to attend Harry and Meghan's wedding.
However, Harry and Meghan's guest list may have an extra touch of Hollywood glamour. The bride's former co-stars from Suits could be making an appearance, including Patrick J. Adams, who played her on-screen husband Mike Ross. Meghan has also remained close friends with Gina Torres, also known as legal eagle Jessica Pearson, and Sarah Rafferty, who stars as Donna Paulsen.
The actress also counts Sophie Ellis-Bextor, Millie Mackintosh, Serena Williams and Priyanka Chopra among her celebrity pals. There has also been talk around whether Barack and Michelle Obama should accept an invite, if they have received one.
One of the most interesting new names to appear on the guest list is Harry's aunt – Sarah, Duchess of York. Prince Andrew's ex-wife was not invited to William and Kate's royal wedding in 2011, given her strained relationship with the royals, namely Prince Philip. However, Sarah has reportedly secured an invite to this upcoming wedding in a bid to heal "broken family ties" and to please Harry's cousins, Princesses Beatrice and Eugenie.
William and Kate's good friend Ellie Goulding had guests on the dance floor at their royal wedding, performing a two-hour set at the evening reception. The Love Me Like You Do singer will most likely be invited to Harry and Meghan's wedding, given her close bond with the royals, although it's not yet known whether she will perform.
Harry may ask his good friend James Blunt, who served with him in the army, to perform, while rumour has it that Ed Sheeran will take to the mic for Harry and Meghan's first dance.
The choice of day
Traditionally, royal weddings are held on a weekday. Prince William and Kate married on a Friday and the nation was given a bank holiday in celebration. Harry and Meghan, meanwhile, will tie the knot on Saturday 19 May. Because Harry will most likely not become King, the public are not being given an extra day off. Harry and Meghan's church ceremony will take place at noon, while William and Kate had a slightly earlier start at 11am.
Given their Windsor choice of venue, the Dean of Windsor, The Rt Revd. David Conner, will conduct Harry and Meghan's service. Their vow exchange will be officiated by The Most Revd. and Rt Hon. Justin Welby, Archbishop of Canterbury.
At William and Kate's wedding, Rowan Williams, the Archbishop of Canterbury at the time, conducted the marriage. The Dean of Westminster, John Hall, presided at the Westminster Abbey service, while Richard Chartres, the Bishop of London, preached the sermon.