John Ernest of Nassau-Siegen (1618–1639)

Count John Ernest of Nassau-Siegen (8 November 1618Jul. – 23 November 1639), Johann Ernst Graf von Nassau-Siegen, official titles: Graf zu Nassau, Katzenelnbogen, Vianden und Diez, Herr zu Beilstein, was a count from the House of Nassau-Siegen, a cadet branch of the Ottonian Line of the House of Nassau. He served as a naval officer in the Dutch West India Company.

Biography
John Ernest was born at  on 8 November 1618Jul. as the seventh and youngest son of Count John VII 'the Middle' of Nassau-Siegen and his second wife, Duchess Margaret of Schleswig-Holstein-Sonderburg. He was baptised in Siegen on 10 January 1619Jul. and was named after his eldest halfbrother John Ernest, who died the previous year.

The will and testament of Count John VII 'the Middle' of 1621 bequeathed John Maurice and his younger brothers from their father's second marriage the district of Freudenberg, some villages in the Haingericht and a third part of the administration of the city of Siegen. After his older half-brother John 'the Younger' had accepted the homage of the city of Siegen for the entire county of Nassau-Siegen on 12 January 1624 and had voluntarily ceded the sovereignty over the Hilchenbach district with and some villages belonging to the  and Netphen districts to his younger brother William on 13/23 January 1624,  John Ernest and his brothers, with the exception of the oldest two brothers John Maurice and George Frederick, accepted only modest appanages.

John Ernest enlisted in the Dutch States Army under Prince Frederick Henry of Orange. He accompanied his eldest brother John Maurice to Dutch Brazil  and served as a naval officer on the 'Alkmaar'. He died of dysentery in São Salvador da Bahia de Todos os Santos  on 23 November 1639 aboard the 'Alkmaar', and was buried in the Calvinist church in Mauritsstad on 1 December.

The first stronghold built by the Dutch in Mauritsstad was named Fortress Ernestus after him.