Lady Arbella Stuart (also Arabella, or Stewart; 1575 – 25 September 1615) was an English noblewoman who was considered a possible successor to Queen Elizabeth I of England.

During the reign of King James VI and I (her first cousin), she married William Seymour, 2nd Duke of Somerset, another claimant to the English throne, in secret.

[2] Her paternal grandparents, the 4th Earl of Lennox and Margaret Douglas, had, of their eight children, two sons who survived childhood: Arbella's father Charles and his older brother Henry Stuart, Lord Darnley, who became the second husband of Mary, Queen of Scots, and the father of Arbella's cousin James VI and I of Scotland, England and Ireland.

[4] During most of her childhood she lived in the protective isolation of Hardwick Hall in Derbyshire with her grandmother, who had married George Talbot, 6th Earl of Shrewsbury, in 1568.

[5] Starting in early 1589 or thereabouts "one Morley ... attended on Arbell and read to her", as reported in a dispatch from Bess of Hardwick to Lord Burghley, dated 21 September 1592.

She also notes he had hoped for an annuity of £40 a year (equivalent to £14,000 in 2023) from Arbella based on the fact that he had "been so much damnified [i.e. that much out of pocket] by leaving the University".

[14] The Venetian ambassador Nicolò Molin described her in 1607, writing that she was 28 (sic)[15] years old, not very beautiful, but highly accomplished in several languages, with refined manners, and always studying.

[18] Other potential matches were the sons of Alexander Farnese, Duke of Parma, who could claim the English throne as descendants of John of Gaunt.

The Pope was reportedly prepared to absolve Odoardo from his obligations but the resistance of Queen Elizabeth I to such a marriage stopped the plan probably even before Arbella could be approached.

He considered the possibility that Elizabeth might allow Arbella Stuart to marry an English husband, and thus "assisted by some domestical match", she might become queen and continue the "sweet pleasing government" of England by a female ruler.

[23] At the end of 1609, Arbella was in trouble for her involvement with an imposter, the "Prince of Moldavia" and other actions deemed suspicious, but she was forgiven, and the King gave her silver plate worth £200 as a New Year's Day gift.

[26] Arbella, who was fourth in line to the English throne, was in trouble again in 1610 for planning to marry William Seymour, then known as Lord Beauchamp, who later succeeded as 2nd Duke of Somerset.

For marrying without his permission, King James imprisoned them: Arbella in Sir Thomas Perry's house in Lambeth and Lord Beauchamp in the Tower of London.

When the King learned of her letters to Lord Beauchamp, however, he ordered Arbella's transfer to the custody of William James, Bishop of Durham.

[29] The black hat and riding safeguard worn by one woman reminded a witness, John Bright, of Moll Cutpurse.

[34] In her final days as a prisoner in the Tower of London, Arbella Seymour (her married name), refusing to eat, fell ill, and died on 25 September 1615.

Emilia Lanier's 1611 poem Salve Deus Rex Judaeorum is dedicated to Arbella among other aristocratic women, though little read at the time.

Lanier recalls a former personal friendship with Arbella that was unrequited; she addresses her as "Great learned Ladie ... whom long I have known but not known so much as I desired".