[1] He was born near Vire as the son of Pierre Le Monnier (1675–1757), who was a scientist himself and a member of the French Academy of Sciences.

[2] In the same year, he also began working at the hospital of Saint Germain en Laye as a physician.

[7] With Claude Richard he was one of the original organizers of Louis XV's botanic collection at Petit Trianon, an undertaking quickly joined by Bernard de Jussieu.

Lemonnier was appointed professor of botany at the Jardin du Roi (later the Jardin des Plantes) in 1759, filling a spot left by the death of Bernard de Jussieu's brother Antoine in April of the previous year.

[8] For Diderot's Encyclopédie he wrote several entries, among them "Electricité", "Magnétisme", "Aimant" (Magnet), and "Aiguille aimantée" (Compass needle).