Prince William Alexander Frederick Ernest Casimir of the Netherlands, Prince of Orange-Nassau (Dutch: Willem Alexander Frederik Ernst Casimir, Prins der Nederlanden, Prins van Oranje-Nassau; Soestdijk Palace, 21 May 1822 – Brussels, 22 October 1822) was the fourth son of the Prince of Orange, later King William II of the Netherlands and his wife Grand Duchess Anna Pavlovna of Russia.

He was baptized on 18 June 1822 in the Nieuwe Kerk, Amsterdam. However, because he had hydrocephalus, he died the same year. He was buried in the Protestant Church in Brussels until his body was transferred to the Royal Crypt in the Nieuwe Kerk, Delft, in 1860.

v t e Dutch princes
Generations indicate descent from William I, the first king of the Netherlands.
1st generation	King William II Prince Frederick
2nd generation	King William III Prince Alexander Prince Hendrik Prince Ernest Casimir
3rd generation	William, Prince of Orange Prince Maurice Alexander, Prince of Orange Hendrik, Prince Consort ¹
4th generation	Bernhard, Prince Consort ¹
5th generation	Claus, Prince Consort ¹
6th generation	King Willem-Alexander Prince Friso ² Prince Constantijn Prince Carlos³ Prince Jaime³ Prince Maurits ⁴ Prince Bernhard ⁴ Prince Pieter-Christiaan ⁴ Prince Floris ⁴
7th generation	Prince Hugo³
¹title granted by Royal Decree to consort of the Queen, without the title "Prince of Orange-Nassau" ²gave up the title "Prince of the Netherlands, but still held the title "Prince of Orange-Nassau" ³title granted by Royal Decree to descendents of Princess Irene ⁴only held the title "Prince of Orange-Nassau"