John Gottlieb Ernestus Heckewelder (March 12, 1743 – January 21, 1823) was an American missionary for the Moravian Church.

Following a visit to Ohio with Christian F. Post, a colonial agent, in 1762 he began temporary employment in the Moravian missions at Friedenshütten and Sheshequin, Pennsylvania.

In 1771, he began his career as an evangelist to the Indians, being appointed assistant to David Zeisberger, in Ohio, where he remained for fifteen years.

Whatever liveth on the land, whatsoever groweth out of the Earth, and all that is in the rivers and waters was given jointly to all and everyone is entitled to his share.

Heckewelder also published Account of the History, Manners, and Customs of the Indian Nations who once inhabited Pennsylvania and the Neighboring States (Philadelphia, 1818; German translation, Göttingen, 1821; French translation, Paris, 1822); Narrative of the Mission of the United Brethren among the Delawares and Mohegan Indians (Philadelphia, 1820); and a collection of Names which the Lenni Lenape or Delaware Indians gave to Rivers, Streams, and Localities within the States of Pennsylvania.