Meghan Markle is a descendant of both King Edward III, and King Henry VIII's third wife Jane Seymour, according to genealogists.
Experts at Ancestry have outlined the American star's links to royal ancestors which stretch back hundreds of years.
Ms Markle's father Thomas Markle is of Dutch and Irish descent, and her mother Doria Ragland is African-American.
Genealogists at Ancestry.co.uk unearthed a calligraphic chart which they used to prove that Meghan is distantly descended from Lionel of Clarence who was the third son of the medieval King Edward III, who ruled England and was Lord of Ireland from 1327 to 1377.
His reign saw the beginning of the Hundred Years War against France, and he created the Order of the Garter in 1348.
St George's Chapel, where Prince Harry and Ms Markle will wed, is the Chapel of the Order of the Garter, the senior order of chivalry in England.
Jane Seymour, Henry VIII's third wife, was Queen of England from 1536 to 1537.
Jane was a second cousin to Isabel Hildyard, Meghan's 12th great-grandmother, Ancestry.co.uk found.
She promoted peace at court, helping to reconcile Henry with his first child, Mary, and was said to be meek and quiet - but is also seen as having manipulated the king into disposing of his second wife Anne Boleyn, to whom she was lady-in-waiting.
She died 12 days after giving birth to Henry VIII's male heir Prince Edward, later Edward VI.
Jane Seymour was said to be the favourite of the king's six wives and the pair are buried together in the Quire of the royal wedding venue St George's Chapel.
Russell James, family history and DNA expert at Ancestry.co.uk, said: "With so many notable royal descendants, we're confident that Meghan is poised to take to her new role with ease and grace.
"The world is clearly watching her every move as she transitions from Hollywood actress to royal duchess."
Meghan's 15th great-grandfather was Sir Phillip Wentworth, a prominent English knight who fought for King Henry IV and was Usher of the King's Chamber, King's Sergeant, Esquire of the Body, King's Carver, and Sheriff of Norfolk and Suffolk.
Robert Hildyard - the 4th cousin of Meghan's eighth great-grandmother - was the Gentleman of the Bedchamber for Charles I.
His duties include waiting on the king when he ate in private, helping him to dress, guarding the bedchamber and water closet, and providing companionship.
Ms Markle, who will be the first mixed race person in modern history to marry a senior British royal, has written of her background.
She described how her great-great-great-grandfather went on to create his own identity when freed from slavery.
"Because in 1865 (which is so shatteringly recent), when slavery was abolished in the United States, former slaves had to choose a name. A surname, to be exact," she wrote.
"Perhaps the closest thing to connecting me to my ever-complex family tree, my longing to know where I come from, and the commonality that links me to my bloodline, is the choice that my great-great-great grandfather made to start anew. He chose the last name Wisdom."