Every engagement ring is special in its own right, but there are some that carry a hidden meaning ¡ª sometimes known only to the bride and groom.
Click through to see some of the royal engagement rings that have more than just sentimental value, and the ones most coveted by royal fans wanting to copy one for their own.
The engagement of Prince William to Kate Middleton was announced by Clarence House on November 16, 2010.
That was the day the world got to see the future Duchess of Cambridge wearing the engagement ring once owned by Princess Diana.
Speaking of the meaningful piece of jewellery, Prince William said: "It's my mother's engagement ring, so of course it's very special to me, and Kate's now very special to me, so it was only right to put the two together."
Kate said, "It's beautiful. It's very, very special".
The ring continues to inspire real-life brides and is now the most Googled royal ring in the UK.
According to data from Design Bundles, there are 32,400 searches for Kate's ring each year.
Other popular royal rings, as seen through internet searches in the UK, are those worn by the Duchess of Sussex, Princess Margaret, Princess Grace of Monaco, and Princess Beatrice and Princess Eugenie.
But outside of the UK, it's Meghan's ring that more brides-to-be are searching for.
The data shows more than 20,000 clicks per month on queries related to Meghan's ring, beating Kate's by a long shot.
The Duchess of Sussex was presented with a sentimental engagement ring by Prince Harry when he proposed in 2017.
The gold ring features a large cushion cut diamond, sourced from Botswana, and two round diamonds from Princess Diana's jewellery collection.
Prince Harry designed the ring with the help of royal jewellers Cleave & Company. It was set in yellow gold, Meghan's favourite metal.
In 2019, Meghan had the ring slightly altered.
The gold band was slimmed down while small, pav¨¦ diamonds were added to the band.
The engagement of the Prince of Wales to Lady Diana Spencer was announced on February 24, 1981.
Princess Diana chose her sapphire and diamond cluster ring out of a catalogue in a break from royal tradition, instead of having it custom-made.
It was made by Garrard, which was appointed Crown Jeweller in 1843.
The ring features a 12-carat Ceylon sapphire surrounded by 14 solitaire diamonds, all set in 18-carat white gold.
The sapphire and diamond cluster design has a special link to Queen Victoria and husband Prince Albert, in the 1840s.
"Prince Albert commissioned a gorgeous blue sapphire and white diamond cluster brooch before his marriage to Queen Victoria, and presented it to her as a wedding gift," Garrard head of design Claire Scott said.
"The Queen wore it on her dress on the day, as her 'something blue'."
That original brooch has remained a favourite of Queen Elizabeth II, who has worn it many times throughout her reign.
Princess Diana made a slight change to her engagement ring, adding six prongs to the existing eight in 1983, to ensure the structural integrity of the sapphire.
The future Queen Elizabeth II announced her engagement to Prince Philip of Greece and Denmark on July 9, 1947, having met 13 years previously at another royal wedding.
Philip had presented his bride with an engagement ring crafted from platinum, featuring a three-carat round brilliant-cut diamond and 10 smaller pav¨¦ set stones on either side.
The ring was designed by Prince Philip with British jeweller Philip Antrobus Ltd, now owned by Pragnell.
And the ring has a special connection with Philip's mother, Princess Alice of Battenberg.
The centre stone was taken from a tiara belonging to Princess Alice, which was given to her as a wedding present by Tsar Nicholas II and Tsarina Alexandra of Russia.
Princess Alice had given her son the tiara so he could provide his wife with a ring fit for a queen.
He also chose to have some of the other diamonds from the antique tiara made into a bracelet, which he gifted to the then-Princess Elizabeth on their wedding day.
Princess Beatrice of York took inspiration from her grandmother the Queen for many parts of her wedding, including her engagement ring.
Much like Queen Elizabeth's, Beatrice's ring features a round brilliant-cut central stone weighing 2.5 carats.
Two baguette diamonds site on either side, weighting .75 carats.
The diamonds were chosen by Beatrice's husband Edoardo Mapelli Mozzi and set in platinum.
The ring - made by British jeweller Shaun Leane - fuses Beatrice and Edoardo's favourite eras: hers, Victorian; his, Art Deco.
Like the diamond in the Duchess of Sussex's ring, Beatrice's is also ethically sourced from Botswana.
Princess Eugenie's engagement ring features a very rare type of stone.
It's an padparadscha sapphire, coveted for its fusion of orange and pink colours.
The sapphire is a cluster design, much like that of Princess Diana's ring, and is surrounded by a halo of white diamonds on a yellow gold band.
In 2018, Eugenie's future husband Jack Brooksbank confirmed he proposed without a ring, as he "didn't want to do anything until Eugenie had signed off on it."
They ended up designing the ring together.
It's thought Eugenie's ring is inspired by the one worn by her mother, Sarah Ferguson.
Prince Rainier III proposed to Grace Kelly with a diamond and ruby eternity band by Cartier, to represent the colours of Monaco's flag.
The red and white stones were reportedly taken from heirlooms from the Monegasque royal family.
Soon before their wedding, Prince Rainier gave his bride a 10.48-carat Cartier ring to go with the band he'd first presented her with.
This new ring featured an emerald cut diamond with two baguette side stones.
Princess Grace wore the larger Cartier ring for most of her life.
Queen Margrethe II of Denmark has one of the most impressive, and unusual engagement rings.
Made by French jewellery house Van Cleef & Arpels, the ring features two large cushion-cut diamonds. They are set diagonally on a yellow gold band.
The style is known as a 'toi et moi' ring - meaning 'you and me' in French.
Actress Megan Fox is the latest celebrity to embrace the unique trend, with fiance Machine Gun Kelly presenting her with an emerald and diamond 'toi et moi' ring.
Eight years before becoming Queen of Denmark, Margrethe was given the ring by French-born diplomat Henri de Laborde de Monpezat. Upon their marriage in 1967, he became known as Prince Henrik.
Queen Margrethe continues to wear her engagement ring, even after the death of Prince Henrik in 2018.
Crown Prince Frederik proposed to Mary Donaldson in 2003 with a ruby and diamond ring.
Mary was given a white gold ring with a central emerald-cut diamond, flanked by two emerald-cut rubies.
The colours ¨C red and white ¨C represent the Danish flag.
After the birth of her twins, Prince Vincent and Princess Josephine in 2011, Mary had another two diamonds added alongside the rubies.
It's thought the four side stones represent the couple's four children, including Prince Christian and Princess Isabella.
Mary's wedding ring is a white gold band with channel-set diamonds.
The Dutch royal family announced the engagement of then-Crown Prince Willem-Alexander and M¨¢xima Zorreguieta in 2001.
The future King Willem-Alexander presented his bride with a ring that has a special link to his royal origins, The House of Orange, of which Dutch royalty descends from.
The centre stone of M¨¢xima's platinum engagement ring is an oval orange diamond with two emerald-cut diamonds.
Two bands encrusted with brilliant-cut diamonds flank the three centre stones.
Her wedding ring is a simple platinum band.
When M¨¢xima married Willem-Alexander in 2002, she became known as the Princess of Orange-Nassau.
Prince Joachim of Denmark chose a ring packed with meaning for his French-born bride, Marie Cavallier.
Her engagement ring features three stones - a diamond, ruby and a sapphire - to represent the colours of the French flag.
The ring is set in a wide, polished yellow gold band.
Joachim, too, shares French roots - his late father, Prince Henrik, was born in the south of France, and Joachim attended boarding school in Paris.
Queen Letizia of Spain was originally presented with an engagement ring featuring 16 baguette-cut diamonds.
The ring was made by Spanish jewellery brand Su¨¢rez.
Letizia does not wear her engagement ring on her right hand much anymore, instead pairing it her yellow gold wedding band on her left hand.
She has been seen with a more elaborate diamond ring on her wedding finger, sparking speculation she's received an upgrade from King Felipe.
Prince Albert of Monaco announced his engagement to Charlene Wittstock on June 23, 2010.
He proposed with a ring from Italian jewellery house Repossi, which is based in Paris.
The central stone is a three-carat pear cut diamond, with smaller pav¨¦ diamonds on either side.
Unfortunately Princess Charlene does not wear her stunning ring all that often, saving it for more formal events.
Camilla, the Duchess of Cornwall, has one of the most impressive engagement rings in the British royal family.
The jewel is a family heirloom, once belonging to Prince Charles' grandmother, Queen Elizabeth the Queen Mother.
The platinum Art Deco ring features a five-carat emerald cut diamond with three baguette cut diamonds on both sides.
The Queen Mother was pictured wearing the stunning ring many times throughout her life.
Camilla pairs the ring with her Welsh gold wedding band.
The Duchess of York chose a Burmese ruby diamond ring when she married Prince Andrew in 1986.
Ten white diamonds surround the red ruby, set on a yellow gold band.
"We came to the mutual conclusion that red was probably the best color for Sarah," the Duke of York said during the couple's engagement interview.
"That's how we came to the choice of the ruby. The extra bits around the outside, we wanted something that was slightly unconventional."