Thatching is the craft of building a roof with dry vegetation such as straw, water reed, sedge, rushes and heather, layering the vegetation so as to shed water away from the inner roof. It is a very old roofing method and has been used in both tropical and temperate climates.

Thatch is still employed by builders in developing countries, usually with low-cost, local vegetation. By contrast in some developed countries it is now the choice of well-to-do people who want their home to have a rustic look.

The tradition of thatching has been passed down from generation to generation for thousands of years, and numerous descriptions of the materials and methods used in England over the past three centuries survive in archives and early publications. In equatorial countries thatch is the prevalent local material for roofs, and often walls.