The Knowledge: How to Rebuild Our World from Scratch is a nonfiction reference work written by astrobiologist Lewis Dartnell. It was published in hardback by The Bodley Head^[1] in the United Kingdom on 3 April 2014 and by The Penguin Press^[2] in the United States on 17 April 2014. The UK paperback was released by Vintage on 5 March 2015 while the US paperback, retitled The Knowledge: How to Rebuild Civilization in the Aftermath of a Cataclysm, was published on 10 March 2015 by Penguin Books.

The book is written as a quick-start guide to restarting civilization following a global catastrophe.

The book describes how humanity and civilization works, and how this it could be altered in the event of worldwide disaster, such as avian flu. Dartnell describes what knowledge would be needed to rebuild civilization as we know it, looking at the history of science and technology.

Dartnell describes a possible 'grace period' in which survivors could salvage food, materials and tools from the ruins of society. However, after a certain point this grace period would end, and humanity would have to produce their own food, make their own tools, practice hygiene and fight infection to maintain health, and develop energy stores for a new society to survive the aftermath.

The book covers topics including agriculture, food and clothing, substances, medicine, and transport. Darnell argues that applying the scientific method to basic knowledge would enable an advanced technological society to reappear within several generations.^[3]