Joan, Countess of Saint-Pol and Ligny (died 18 September 1430, Avignon), called the Demoiselle de Luxembourg, was the ruling Count of Saint Pol and Count of Ligny in 1430.
She was the daughter of Guy of Luxembourg, Count of Ligny and Mahaut of Châtillon, Countess of Saint-Pol.
She was living at the time at Beaurevoir, which belonged to her favourite nephew John.
The Demoiselle de Luxembourg showed kindness to her and pleaded with her nephew not to sell Joan to the English, giving him a promise to make him her heir if he did not.
The Demoiselle is a character in Philippa Gregory's 2011 historical novel The Lady of the Rivers, which centres on her great-niece Jacquetta of Luxembourg.