|Mother Gertrude of Hanau||Name Maria Hanau-Horowitz|
|Father Frederick William I, Elector of Hesse|
Born 22 August 1839 Schloss Wilhelmshohe (1839-08-22)
Died 26 March 1917(1917-03-26) (aged 77) Bonn
Princess Maria of Hanau and Hořowitz (22 August 1839 – 26 March 1917) was the youngest daughter of Frederick William, Elector of Hesse-Kassel (1802–1875), and his morganatic wife, Gertrude Falkenstein (1803–1882), whom he later elevated to Princess of Hanau and Hořowitz (German: Fürstin von Hanau und zu Hořowitz).
Prince Frederick of Holstein asked for Princess Maria's hand, but he was rejected. On 27 December 1857 she married Prince William of Hesse-Philippsthal-Barchfeld (3 October 1831, Burgsteinfurt – 17 January 1890, Rotenburg), son of Landgrave Charles. With this marriage, her mother hoped to bind her family closer to the House of Hesse; the Grand Duke of Hesse-Darmstadt, however, regarded William's marriage as morganatic and refused to acknowledge the five children from this marriage as Hessian princes. The children nevertheless used their father's style and title.
Maria divorced on 18 March 1872. She and her two surviving daughters moved to Wiesbaden. She continued to style herself Princess of Hesse, and got into a dispute about her title with Frederick William, the former heir presumptive of Hesse-Kassel, who held that she'd lost the right to use that title due to her divorce. After she lost the court case, she asked Emperor William I to provide her with a new title. The imperial court sent her a list of castles in Nassau to choose from — apparently court officials in Berlin were confused about the various former principalities that made the new Hesse-Nassau province — and she chose Ardeck. Ardeck Castle is a ruin near Holzheim, which is situated in today's Rhein-Lahn-Kreis. From 28 July 1876, she and her children were styled Princess of Ardeck and Princes of Ardeck.
She later moved to Bonn, where she died in 1917.