Catherine Lucy Wilhelmina Powlett, Duchess of Cleveland (née Stanhope; 1 June 1819 – 18 May 1901), also known as Lady Dalmeny and Lady Harry Vane, was an English courtier, historian and genealogist, best known for her 1889 work The Battle Abbey Roll with some Account of the Norman Lineages.

By her first marriage to Lord Dalmeny, she was the mother of Prime Minister Archibald Primrose, 5th Earl of Rosebery.

At the time of Queen Victoria's accession, the 18-year-old Lady Wilhelmina was regarded as one of the most beautiful woman at court.

Shortly before her 88th birthday, Lady Cleveland unexpectedly died of a cardiac arrest in Wiesbaden, Hesse, a week after undergoing successful eye surgery.

"In spite of her advanced age the Duchess of Cleveland was an indefatigable traveller, and her faculties and interests remained undimmed," reported The Times in her obituary.