Namesakes
French Presidents and Prime Ministers:
1 prime minister
(prime minister) Armand-Emmanuel de Vignerot du Plessis 1815-1818; 1820-1821 
Notable Athletes:
2 rugby, 1 cricket
(rugby) Jannie du Plessis 1982-
(rugby) Bismarck du Plessis 1984-
(cricket) Faf du Plessis 1984-
Notable Politicians and Statespeople:
1 politician
Cardinal Richelieu (a.k.a. du Plessis) 1585-1642