Happy Birthday: Lucy Christiana, Lady Duff-Gordon (née Sutherland; 13 June 1863 – 20 April 1935) was a leading British fashion designer in the late 19th and early 20th centuries who worked under the professional name Lucile.

The first British-based designer to achieve international acclaim, Lucy Duff-Gordon was a widely acknowledged innovator in couture styles as well as in fashion industry public relations. In addition to originating the "mannequin parade", a precursor to the modern fashion show, and training the first professional models, she launched slit skirts and low necklines, popularized less restrictive corsets, and promoted alluring and pared-down lingerie.

Opening branches of her London house, Lucile Ltd, in Chicago, New York City, and Paris, her business became the first global couture brand, dressing a trend-setting clientele of royalty, nobility, and stage and film personalities. Duff-Gordon is also remembered as a survivor of the sinking of the RMS Titanic in 1912, and as the losing party in the precedent-setting 1917 contract law case of Wood v. Lucy, Lady Duff-Gordon, in which Judge Benjamin N. Cardozo wrote the opinion for New York's highest court, the New York Court of Appeals, upholding a contract between Duff-Gordon and her advertising agent that assigned the agent the sole right to market her name. It was the first case of its kind; clothes were labelled and sold at a lowered cost in a cheaper market under an expensive "brand name".

The Titanic episode is one of the most prominent aspects of Lucy Duff-Gordon's life, thanks partly to motion pictures. The films, however, portrayed her without great attention to accuracy. She has been portrayed by Harriette Johns in A Night to Remember (1958); by Rosalind Ayres in James Cameron's epic Titanic (1997); and by Sylvestra Le Touzel in the British miniseries Titanic (2012). She is also a key character in the novel The Dressmaker, by Kate Alcott, which portrays both the sinking of the Titanic and the negative publicity that followed for the Duff-Gordons.

Lucy Duff-Gordon had another close call three years after surviving the Titanic, when she booked passage aboard the final voyage of the RMS Lusitania. It was reported in the press that she cancelled her trip due to illness. The Lusitania was sunk by a German torpedo on 7 May 1915.