Le Monnier or Lemonnier may refer to:
- People
- André Lemonnier (1896–1963), French admiral
- Anicet Charles Gabriel Lemonnier (6 June 1743 - 17 August 1824), a well-known French painter of historical subjects
- Emile-René Lemonnier (1893–1945), French general
- Louis Guillaume Le Monnier (1717–1799), French natural scientist, brother of Pierre Charles
- Pierre Lemonnier (1675–1757), French astronomer, father of Pierre Charles and Louis Guillaume
- Pierre Charles Le Monnier (1715–1799), French astronomer, brother of Louise Guillaume
- Other
- Le Monnier (crater), lunar crater named after Pierre Charles Le Monnier
- Camp Lemonnier, United States Naval Expeditionary Base in Djibouti, named after Emile-René Lemonnier.