John Henry Mohrmann was an American-Belgian Marine painter and ship portrait painter.

John Henry Mohrmann was born Johann Hinrich in Estebrügge Mohrmann, near Hannover (Germany). He was the son of Henry Mohrmann and Anna Meyer, the family immigrated to San Francisco when he was two years old. His father was a magistrate in Oakland. His mother died when he was ten years old. He married on May 7, 1886 by Juana Meyer of Fray Bentos in Uruguay between 1888 and 1908 and had seven children together.

Mohrmann worked as sailer, stage designer and restorer before settling in Antwerp in 1884 where he soon became a sought after ship portrait painter. He emigrated to Canada in 1913. His works are considered to be among the best achievements of the genre before painted ship portraits were superseded by photography.