Year 1451 (MCDLI) was a common year starting on Friday of the Julian calendar.
Henry II "the Rich" of Nassau, German: Heinrich II. "der Reiche" von Nassau was Count of Nassau. He distinguished himself in particular by his chivalrous and devout spirit. He was charitable and made great donations to the church, so that the monasteries and prayer houses in the area of present-day Nassau experienced the most significant bloom in his time. The greatest favour was the Teutonic Order to enjoy, to which he donated especially for the renunciation of his brother's, upon his entry into the order. Henry participated in the Sixth Crusade. He was the builder of the castles Sonnenberg, Ginsburg and Dillenburg.
The House of Sponheim or Spanheim was a medieval German noble family, which originated in Rhenish Franconia. They were immediate Counts of Sponheim until 1437 and Dukes of Carinthia from 1122 until 1269. Its cadet branches ruled in the Imperial County of Ortenburg-Neuortenburg and various Sayn-Wittgenstein states until 1806.
Count John V of Nassau-Siegen, German: Johann V. Graf von Nassau-Siegen, official titles: Graf zu Nassau, Vianden und Diez, Herr zu Breda, was since 1475 Count of Nassau-Siegen and of half Diez. He descended from the Ottonian Line of the House of Nassau.
Margaret, Marchioness of Namur was ruling Marchioness of Namur, from 1229 to 1237. She was the daughter of Peter of Courtenay, Latin Emperor of Constantinople (1216-1219) and Yolanda of Flanders. By marriage to Henry I, Count of Vianden, she was Countess-consort of Vianden.
Count John IV of Nassau-Siegen, German: Johann IV. Graf von Nassau-Siegen, official titles: Graf zu Nassau, Vianden und Diez, Herr zu Breda, was since 1442 Count of Nassau-Siegen, of Vianden and of half Diez, and Lord of Breda and of the Lek. He descended from the Ottonian Line of the House of Nassau.
Count John I of Nassau-Siegen, German: Johann I. Graf von Nassau-Siegen, was since 1362 Count of Nassau-Siegen. He descended from the Ottonian Line of the House of Nassau.
Count Otto II of Nassau-Siegen, German: Otto II. Graf von Nassau-Siegen, was since 1343 Count of Nassau-Siegen. He descended from the Ottonian Line of the House of Nassau.
Adolph II of the Marck was Count of the Marck.
Count Adolf I of Nassau-Siegen, German: Adolf I. Graf von Nassau-Siegen, was since 1384 Count of Diez, through his first marriage. With his brothers, he succeeded his father in 1416 as Count of Nassau-Siegen, and also inherited the County of Vianden in 1417. He descended from the Ottonian Line of the House of Nassau.
Count John II with the Helmet of Nassau-Siegen, German: Johann II. mit der Haube Graf von Nassau-Siegen, succeeded, with his brothers, his father in 1416 as Count of Nassau-Siegen. With his brothers, he inherited the County of Vianden in 1417, and also inherited half of the County of Diez in 1420. He descended from the Ottonian Line of the House of Nassau.
Lady Mary of Looz-Heinsberg, Dutch: Maria van Loon-Heinsberg, was a noble lady from the House of Looz and through marriage Countess of Nassau-Siegen.
Henry VIII (1465–1513) was a count of Waldeck and the founder of the older line of Waldeck-Wildungen. He was also temporarily governor of the County of Vianden, a possession of the House of Nassau.
Margaret of Cleves, also spelled Margaretha or Margarethe was the wife of Count Adolf II of the Marck and mother of Adolf III of the Marck. She was a daughter of Count Dietrich VIII of Cleves and Margaret of Guelders, who was a daughter of Reginald I of Guelders.
Landgravine Elisabeth of Hesse-Marburg, German: Elisabeth Landgräfin von Hessen-Marburg, was a landgravine from the House of Hesse-Marburg and through marriage Countess of Nassau-Siegen. She was heiress to the County of Katzenelnbogen, which after her brother's death was claimed both by her and the Landgraviate of Hesse. The legal dispute for the County of Katzenelnbogen between the House of Nassau and the House of Hesse lasted until well after her death and is known as the Katzenelnbogische Erbfolgestreit.
Count John III the Younger of Nassau-Siegen, German: Johann III. der Jüngere Graf von Nassau-Siegen, succeeded, with his brothers, his father in 1416 as Count of Nassau-Siegen. With his brothers, he inherited the County of Vianden in 1417, and also inherited half of the County of Diez in 1420. He descended from the Ottonian Line of the House of Nassau.
Henry I (c.1200–1252) was the hereditary Count of Vianden from 1210 and, through his wife, Marquis of Namur from 1229.
Marie of Namur, also known as Marie de Namur or Maria van Dampierre. Her titles were Gräfin von Vianden, from her first marriage and Dame de Pierrepont, from her second marriage to, Theobald of Bar.
The House of Nassau-Corroy is a bastard branch of the House of Nassau. Unlike the main branch of the House of Nassau, this illegitimate branch was faithful to the king of Spain and Roman Catholic.
Countess Adelaide of Vianden was a countess from the House of Vianden, the cadet branch of the House of Sponheim that ruled the County of Vianden, and through marriage Countess of Nassau-Siegen. She acted as regent of the County of Nassau-Siegen for her eldest son in the period 1351–1362.
