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
- Jean Delannoy, actor and film director
- Louis De Lannoy, cyclist
- Luc Delannoy, writer and philosopher
- Philip de Lannoy, Prince of Sulmona, military leader
- Countess Stéphanie de Lannoy, now the Hereditary Grand Duchess of Luxembourg
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