De Lannoy or Delannoy is a surname, and may refer to;

Noble Belgian House of Lannoy

• Jean de Lannoy
• Baldwin of Lannoy
• Hugo van Lannoy
• Guillebert de Lannoy, soldier, traveller and diplomat
• Charles de Lannoy, 1st Prince of Sulmona: soldier and statesman
• Philip de Lannoy, 2nd Prince of Sulmona, military leader
• Countess Stéphanie de Lannoy, now the Hereditary Grand Duchess of Luxembourg

Others

• Albert Delannoy, long jumper
• Colinet de Lannoy, composer
• Eustachius De Lannoy, naval commander
• Henri Delannoy (1833–1915), French military officer and amateur mathematician
• Jean Delannoy, actor and film director
• Louis De Lannoy, cyclist
• Luc Delannoy, writer and philosopher
• Marcel Delannoy (1898–1962), French composer
• Claire Delannoy, French writer
• Robert Delannoy, World War I flying ace

See also

• Delano family
• Delannoy numbers, a mathematical sequence named after Henri Delannoy
• Delaunay
• Delone (disambiguation)
• Lannoy (disambiguation)