Johannes Gerardus Keuleman was a Dutch bird illustrator. For most of his life he lived and worked in England, illustrating many of the best-known ornithology books of the nineteenth century.

Keulemans was born in Rotterdam. As a young man he collected animal specimens for museums such as the Natural History Museum in Leiden, whose director, Hermann Schlegel, encouraged Keulemans and sent him on the 1864 expedition to West Africa. In 1869, he was persuaded by Richard Bowdler Sharpe to illustrate his Monograph of the Alcedinidae, or Family of Kingfishers (1868-1871) and to move to England, where he lived for the rest of his life.

He was married twice, and had eight children by his first wife and seven children by his second wife. Only nine of his children reached adulthood. He also wrote topics on spirituality, and claimed he had a premonition at the moment of death of one of his sons. He died in Ilford, Essex (now part of Greater London) and is buried in Buckingham Road cemetery, Ilford, in an unmarked grave.