De Lannoy or Delannoy is a surname, and may refer to;
Albert Delannoy, long jumper
Charles de Lannoy, soldier and statesman
Colinet de Lannoy, composer
Eustachius De Lannoy, naval commander
Guillebert de Lannoy, traveller and diplomat
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
Philip de Lannoy, Prince of Sulmona, military leader
Countess Stéphanie de Lannoy, now the Hereditary Grand Duchess of Luxembourg
