Diederik is a Dutch male given name. People with the name include:

• Diederik Aerts (born 1953), Belgian theoretical physicist
• Diederik Bangma (born 1990), Dutch football goalkeeper
• Diederik Boer (born 1980), Dutch footballer
• Diederik Boomsma (born 1978), Dutch politician
• Diederik van Dijk (born 1971), Dutch politician
• Diederik van Domburg (1685–1736), Dutch governor of Ceylon
• Diederik Durven (1676–1740), Dutch Governor-General of the Dutch East Indies
• Diederik Foubert (born 1961), Belgian cyclist
• Diederik Jansz. Graeff (1532–1589), Dutch merchant, ship-owner and politician
• Diederik Grit (1949–2012), Dutch translator and translation scholar
• Diederik Hol (born 1972), Dutch design engineer
• Diederik Korteweg (1848–1941), Dutch mathematician
• Diederik Jekel (born 1984), Dutch science journalist and television presenter
• Diederik Johannes Opperman (1914–1985), Afrikaans poet
• Diederik van Rooijen (born 1975), Dutch film director
• Diederik Samsom (born 1971), Dutch politician
• Diederik van Silfhout (born 1988), Dutch Olympic dressage rider
• Diederik Simon (born 1970), Dutch rower
• Diederik Sonoy (1529–1597), Dutch rebel leader during the Eighty Years' War
• Diederik Stapel (born 1966), Dutch social psychologist
• Diederik Tulp (1624–1682), Dutch merchant
• Diederik Jacob van Tuyll van Serooskerken (1772–1826), Dutch nobleman, later Russian major general and ambassador
• Diederik van Weel (born 1973), Dutch field hockey player
• Diederik Wissels (born 1960), Dutch jazz pianist

• Diederik cuckoo, in which Diederik is an onomatopoeic rendition of the bird's call
• Diedrick, given name and surname
• Theodoric