Abstract: A three-piece heat resistant gasket having a rigid body molded of heat insulating material forming a relatively thin web around the fluid passage to be sealed. Two resiliently compressible gasket elements in the form of flat slabs of heat insulating materials are secured to the opposite faces of the web around the fluid passage, with their outer faces lying slightly above bolt hole-containing bosses, formed as part of the body, which limit the compression of the gasket elements. The provision of a large number of small cavities in the web, which are closed by the gasket elements, significantly reduces the rate of heat transfer through the gasket.