Jacob Knapp (December 7, 1799, Otsego County, New York - March 2, 1874, Rockford, Illinois) was a popular Baptist preacher of the 19th-century United States.

From there he moved to Watertown, New York, where he was also at the same time pastor of a church and manager of a large farm, displaying a full degree of energy and capacity in each occupation.

He gave up his secular employment, and undertook a wider work as an evangelist.

In Baltimore, Boston, and New York, vast numbers attended his preaching, and such excitement prevailed that mobs threatened him and his hearers, and the protection of the civil authorities was necessary.

In his old age he had acquired, by several judicious business investments, a comfortable competency, which he proposed shortly before his death to distribute among the benevolent societies of his church.