Louise Juliana of Orange-Nassau (31 March 1576 in Delft – 15 March 1644 in Königsberg) was a countess of the Palatinate by marriage to Frederick IV, Elector Palatine, and regent during the minority of her son from 1610 until 1611.
She was the eldest daughter of William of Nassau, Prince of Orange and his third spouse Charlotte de Bourbon-Montpensier.