Charlotte Williams-Wynn (née Grenville; c. 1754 – 29 September 1830) was a British aristocrat.
Williams-Wynn was born in Llanforda, Oswestry. She was the eldest child of the Prime Minister George Grenville and his wife Elizabeth, daughter of the Tory statesman Sir William Wyndham, Bt, and she was related to the two Prime Minister William Pitts through her paternal aunt Hester Grenville who married Pitt the Elder (the 1st Earl of Chatham) and became mother of William Pitt the Younger. Her mother and father died in 1769 and 1770 respectively, and guardianship of their daughter Charlotte was assumed by George's elder brother, Richard Grenville-Temple, 2nd Earl Temple. In December 1771, she married Sir Watkin Williams-Wynn, 4th Baronet, and became known as Lady Williams-Wynn. The couple had eight children, six of whom survived to adulthood, including Sir Watkin Williams-Wynn, 5th Baronet and Charles and Henry Williams-Wynn. Upon her husband's death, Lady Williams-Wynn became the sole administrator of his Welsh estates under the terms of his will and functioned as such until her eldest son reached the age of majority.