Catherine of Nassau-Dillenburg (29 December 1543 at Dillenburg Castle in Dillenburg – 25 December 1624 in Arnstadt) was a daughter of William I, Count of Nassau-Siegen and his second wife, Juliana of Stolberg.
In 1560, she married Günther XLI, Count of Schwarzburg-Arnstadt and she moved with her husband to Arnstadt.
She then took Catharina Belgica, a daughter of William and Charlotte of Bourbon, with her to Arnstadt.
In 1593, she tried to settle a dispute between Maria of Nassau and Maurice, Prince of Orange over the legacy of their father William.
She was not successful, but did succeed in mediating between Louise de Coligny and John VI, Count of Nassau-Dillenburg, who had disagreed over the future marriages of William's six daughters by Charlotte of Bourbon.