Denis Diderot's middle name is not commonly known or documented. In fact, he is typically referred to simply as "Denis Diderot" without a middle name. It is important to note that in the 18th century, middle names were not as commonly used as they are today, especially in France where Diderot lived.
Denis Tuohy's birth name is Denis John Tuohy.
Denis Vaughan's birth name is Denis Edward Vaughan.
Denis Sukhanov's birth name is Denis Valeryevich Sukhanov.
Denis Avey's birth name is George Denis Avey.
Catalina Denis's birth name is Catalina Zarate Denis.
Denis Evstigneev's birth name is Denis Evgenevich Evstigneev.
Denis Forman's birth name is John Denis Forman.
Denis Pervoikin's birth name is Denis Sergeevitch Pervoikin.
Denis Netto's birth name is Denis Souza Netto.
Denis Norden's birth name is Denis Mostyn Norden.
Denis Menke's birth name is Denis John Menke.
Denis Constanduros's birth name is Denis Stephanos Constanduros.