De Ridder is a Dutch surname, meaning "the knight". It may refer to:

• Alexandra Simons de Ridder (born 1963), German equestrian
• Alfons de Ridder (1882–1960), Flemish writer and poet
• Allard de Ridder (1887–1966), Dutch and Canadian conductor, violist, and composer
• André de Ridder (born 1971), German music conductor
• Chantal de Ridder (born 1989), Dutch footballer
• Daniël de Ridder (born 1984), Dutch footballer
• Daniela De Ridder (born 1962), German politician
• Dirk de Ridder (sailor) (born 1972), Dutch competitive sailor
• Gaspard Deridder (1918–1977), Belgian boxer
• Hilde De Ridder-Symoens (1943–2023), Dutch historian
• Johan de Ridder (1927–2013), South African architect
• Louis De Ridder (1902–1981), Belgian winter sports athlete
• Luis de Ridder (1928–2004), Argentine alpine skier
• Marcello de Ridder (1922–1973), Argentine bobsledder
• Minneke De Ridder (born 1980), Belgian politician
• Paul De Ridder [de; fr; nl] (born 1948), Belgian historian and politician
• Peter de Ridder (born 1946), Dutch businessman and sailor
• Philippe De Ridder (born 1964), Belgian football player, coach, and administrator
• Reinier De Ridder (born 1990), Dutch mixed martial artist
• Steve De Ridder (born 1987), Belgian footballer
• Willem de Ridder (1939–2022), Dutch artist and anarchist

• DeRidder, Louisiana, a place named for Ella de Ridder, the sister-in-law of a Dutch railroad financier