| Frederick Louis of Nassau-Ottweiler | |
| Noble Family: | House of Nassau |
| Father: | John Louis, Count of Nassau-Ottweiler |
| Mother: | Countess Palatine Dorothea Catherine of Birkenfeld-Bischweiler |
| Spouse: | Christiane of Ahlefeldt-Rixingen Louise Sophie of Hanau-Lichtenberg |
| Birth Place: | Ottweiler |
| Death Place: | Saarbrücken |
Frederick Louis of Nassau-Ottweiler (13 November 1651 - 25 May 1728) was a member of the House of Nassau.
He was born in Ottweiler, the son of John Louis, Count of Nassau-Ottweiler and Countess Palatine Dorothea Catherine of Birkenfeld-Bischweiler. He was count of Nassau-Ottweiler from 1680 until his death. From 1721, he was also Count of Nassau-Idstein; from 1723 also Count of Nassau-Saarbrücken. When he died in Saarbrücken, without a male heir, his territories fell to his cousin Charles of Nassau-Usingen after his death in 1728.
Frederick Louis married on 28 July 1680 with Countess Christiane von Ahlefeldt (1659–95), the daughter of Count Friedrich von Ahlefeldt and his first wife Countess Margarethe Dorothea zu Rantzau (1642-1665). They had eight daughters:
After Christiane's death, Frederick Louis married on 27 September 1697 Countess Louise Sophie of Hanau-Lichtenberg (11 April 1662 in Bischofsheim am Hohen Steg - 9 April 1751 in Ottweiler), the daughter of Johann Reinhard II of Hanau-Lichtenberg and Countess Palatine Anna Magdalena of Birkenfeld-Bischweiler. This marriage produced one child, a stillborn son, in 1698.