The Honorable Nellie Ionides (born Nellie Samuel; 1883 – 15 November 1962) was an English collector, connoisseur and philanthropist. She is best known for saving the 18th-century Octagon Room at Orleans House in Twickenham from destruction, and for donating this and also many pieces from her extensive art collection to the local council (now the London Borough of Richmond upon Thames).