Petronilla Melusina von der Schulenburg, Countess of Walsingham, Countess of Chesterfield (1 April 1693 – 16 September 1778) was the natural daughter of King George I of Great Britain and his longtime mistress, Melusine von der Schulenburg, Duchess of Kendal.

In 1722, Melusina was created Baroness Aldborough and Countess of Walsingham as a life peer.

After the death of her father in 1727, she lived mainly with her mother at Kendal House in Isleworth.

In Isleworth, Middlesex, on 5 September 1733 Melusina married Philip Stanhope, 4th Earl of Chesterfield, a leading Whig politician.

[1] Calvert was born in England in around 1730–32, the illegitimate son of the 5th Baron Baltimore, while his mother's identity is otherwise unknown.