In the Genesis Flood story, pitch covered Noah's Ark on the inside and outside to make it watertight.
Genesis 6:14 instructs Noah to make rooms in the Ark and cover it with pitch inside and out. The Hebrew term translated as pitch is related to bitumen or a waterproofing substance. The text does not specify a modern chemical formula, a particular tree, or a named commercial product.
Pitch was a familiar ancient waterproofing material. Bitumen and related substances were used in the ancient Near East to seal boats, baskets, buildings, and other objects against water. This detail connects the Ark story with practical boatbuilding techniques known in the region.
The material is sometimes confused with the Ark's construction wood. Genesis separately mentions the wood used for the vessel and the pitch used to seal it. It also does not say that pitch formed the Ark's structural frame; its stated function was waterproofing the interior and exterior surfaces.