| Duke of Mercœur | |
| Nicolas | |
| Birth Date: | 16 October 1524 |
| House: | House of Lorraine |
| Birth Place: | Bar-le-Duc, France |
| Issue: | Louise, Queen of France and Poland Philippe Emmanuel, Duke of Mercœur Charles, Cardinal of Vaudémont Marguerite, Duchess of Joyeuse and Piney François, Marquis of Chaussin Henri, Marquis de Mouy and Count of Chaligny Antoine, Bishop of Toul Eric, Bishop of Verdun |
| Full Name: | French: Nicolas de Lorraine |
| Spouse: | Marguerite d'Egmont Joanna of Savoy Catherine of Lorraine |
| Father: | Antoine, Duke of Lorraine |
| Mother: | Renée de Bourbon |
Nicolas of Lorraine, Duke of Mercœur (16 October 1524 – 23 January 1577), was the second son of Antoine, Duke of Lorraine, and Renée de Bourbon.
He was originally destined for an ecclesiastical career, being made bishop of Metz in 1543 and of Verdun in 1544. In June 1545, he became joint "tutor and administrator" for his nephew, Charles III, Duke of Lorraine, with his sister-in-law Christina of Denmark. However, the Estates of Lorraine, in November 1545, removed him in favor of Christina as sole regent. He opposed her pro-Imperial policies. Resigning his dioceses in 1548 in favor of his uncle Jean, Cardinal of Lorraine, he took the title Count of Vaudémont.
After seizure of the Three Bishoprics in 1552 by Henry II of France, he was re-appointed as sole regent for his nephew, a position he retained until 1559.
Nomeny was detached from the Bishopric of Metz in 1551 and given to him as a margraviate by Maximilian II, Holy Roman Emperor, in 1567, in right of which he was recognized as an independent, hereditary Prince of the Empire (the House of Lorraine would obtain a full vote in the Imperial Diet in 1736 for Nomeny in compensation for cession of the Duchy of Lorraine to France—in addition to acquisition of the Grand Duchy of Tuscany).
In France, his mother's barony of Mercœur was likewise elevated to the status of a princedom (though not independent of the French crown) in 1563, and raised to a ducal peerage in 1569. He was also created a knight of the Order of Saint Esprit.
He married three times. His first marriage, on 1 May 1549 in Brussels, was to Countess Marguerite d'Egmont (1517 – 10 March 1554, Bar-le-Duc), daughter of Count Jean IV of Egmont. They had:
His second marriage was on 24 February 1555 at Fontainebleau, to Princess Joanna of Savoy-Nemours (1532–1568), daughter of Philippe, Duke of Nemours. By this marriage they had:
His third marriage was on 11 May 1569 at Reims, to Princess Catherine of Lorraine-Aumale (1550–1606), daughter of Claude, Duke of Aumale. They had: