Megastructures is a documentary television series appearing on the National Geographic Channel in the United States and the United Kingdom, Channel 5 in the United Kingdom, France 5 in France, and 7mate in Australia.

Each episode is an educational look of varying depth into the construction, operation, and staffing of various structures or construction projects, but not ordinary construction products.

Generally containing interviews with designers and project managers, it presents the problems of construction and the methodology or techniques used to overcome obstacles. In some cases (such as the Akashi-Kaikyo Bridge and Petronas Towers) this involved the development of new materials or products that are now in general use within the construction industry.

Megastructures focuses on constructions that are extreme; in the sense that they are the biggest, tallest, longest, or deepest in the world. Alternatively, a project may appear if it had an element of novelty or are a world first (such as Dubai's Palm Islands). This type of project is known as a megaproject.

The series follows similar subjects as the History Channel's Modern Marvels and Discovery Channel's Extreme Engineering, covering areas of architecture, transport, construction and manufacturing.