François Leclerc du Tremblay (4 November 1577 – 17 December 1638), also known as Père Joseph, was a French Capuchin friar, confidant and agent of Cardinal Richelieu.

[1] He was the original éminence grise—the French term ("grey eminence") for a powerful advisor or decision-maker who operates secretly or unofficially.

[3] The description drew on the grey friar's cloak that Père Joseph wore and the title "eminence" conferred on Richelieu as a cardinal.

For Richelieu, he maneuvered at the Diet of Regensburg to thwart the aggression of the Habsburg emperor, and then recommended the intervention of Gustavus Adolphus, and the Protestant armies, thereby maintaining a balance of power.

The story that Richelieu visited him when on his deathbed and roused the dying man by the words, "Courage, Father Joseph, we have won Breisach", is apocryphal.