Eugène Lemercier (7 November 1886 – 6 April 1915) was a French artist and soldier in World War I.

His letters to his mother are a first-hand account of the war, and are preserved in the National Library of Ireland.

Lemercier won a number of government prizes for his paintings between 1906 and 1914, for pieces such as La Contemplation (Study for 'Contemplation'), which is held by the National Gallery of Ireland.

During September and October, Lemercier was in what he called "the zone of the horrors", during which time he received no correspondence and he wrote in his diary.

His writings are held by the National Library of Ireland (NLI), as a first-hand testimony of the war.