John Émile Lemoinne (October 17, 1815 - December 14, 1892) was a French journalist.

He was born of French parents in London. He was educated first at an English school and then in France. In 1840 he began writing for the Journal des débats, on English and other foreign questions, and under the empire he held up to admiration the free institutions of England by contrast with imperial methods. After 1871 he supported Thiers, but his sympathies rather tended towards a liberalized monarchy, until the comte de Chambord's policy made such a development an impossibility, and he then ranged himself with the moderate republicans.

In 1875 Lemoinne was elected to the French Academy, and in 1880 he was nominated a life senator. Distinguished though he was for a real knowledge of England among the French journalists who wrote on foreign affairs, his tone towards English policy greatly changed in later days, and though he never shared the extreme French bitterness against England as regards Egypt, he maintained a critical attitude which served to stimulate French Anglophobia. He was a frequent contributor to the Revue des deux mondes, and published several books, the best known of which is his Études critiques et biographiques (1862). He died in Paris on the 14th of December 1892.