Johan van Oldenbarnevelt, Lord of Berkel en Rodenrijs (1600), Gunterstein (1611) and Bakkum (1613) (September 14, 1547, Amersfoort – May 13, 1619, The Hague) is a Dutch politician who played an important role in the Dutch struggle for independence from Spain.

Van Oldenbarnevelt had studied law at Leuven, Bourges, Heidelberg and Padua, and traveled in France and Italy before settling in The Hague.

A Calvinist, he supports William the Silent in his revolt against Spain, and fights in William's army.