John III, Count of Nassau-Beilstein

John III, Count of Nassau-Beilstein (1490 – 11 December 1561) was a son of John II and his wife Maria of Solms-Braunfels.

In 1513, he succeeded his father as Count of Nassau-Beilstein. In 1523, he married Anna (1505–1564), a daughter of Louis I (1473–1523) of Nassau-Weilburg and Margaret of Nassau-Wiesbaden (1487–1548).

He died on 11 December 1561. As he had no male heir, Nassau-Beilstein fell back to Nassau-Dillenburg. He may have had a son, Jonas/Hans, but more documentation is needed to confirm. It is unclear why this son, if he existed, did not inherit his father's title.