Martha Furnace is an abandoned iron furnace in Burlington County, New Jersey, in the New Jersey Pine Barrens. It operated between 1793 and the mid-1840s, using charcoal fuel and locally-mined bog iron to make a variety of cast products as well as pig iron. For most of its operating history, it was principally owned by the New Jersey ironmaster Samuel Richards and managed by Jesse Evans. The settlement that grew up around it was abandoned after ironmaking ceased, and the site of the furnace now lies undeveloped in Wharton State Forest.