Cecilia Underwood, Duchess of Inverness (née Gore and formerly Buggin; c. 1789 – 1 August 1873) was the second wife of Prince Augustus Frederick, Duke of Sussex (sixth son of King George III).

Her father, Arthur Gore, was the 2nd Earl of Arran, a prominent member of 'the Ascendancy', the Anglo-Irish aristocracy; her mother was Elizabeth née Underwood.

[1] She later married Prince Augustus Frederick, Duke of Sussex,[1] the sixth son of George III, at Great Cumberland Place, London, on 2 May 1831.

However the Duke of Sussex's second marriage also contravened the Act for failure to seek permission, making it also legally void.

As the marriage was not lawful, Lady Cecilia could not take the style and title Her Royal Highness The Duchess of Sussex.

To compensate for this, in 1840 Queen Victoria created her Duchess of Inverness,[3] in her own right, with remainder to the heirs male of her body lawfully begotten.