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 Jacques Delannoy (1912–1958), French footballer Jean Delannoy, actor and film director Louis De Lannoy, cyclist , writer and philosopher Marcel Delannoy (1898–1962), French composer Claire Delannoy, French writer Robert Delannoy, World War I flying ace
Sandra Delannoy, French politician
See also Delano family Delannoy numbers, a mathematical sequence named after Henri Delannoy
Lannoy (disambiguation)