The memex (a portmanteau of "memory" and "index") is the name given by Vannevar Bush to the hypothetical proto-hypertext system he described in his 1945 The Atlantic Monthly article As We May Think (AWMT). Bush envisioned the memex as a device in which individuals would compress and store all of their books, records, and communications, "mechanized so that it may be consulted with exceeding speed and flexibility". The memex would provide an "enlarged intimate supplement to one's memory". The concept of the memex influenced the development of early hypertext systems (eventually leading to the creation of the World Wide Web) and personal knowledge base software.

In Bush's 1945 paper, he describes a memex as an electromechanical device that individuals could use to read a large self-contained research library, and add or follow associative trails of links and notes created by that individual, or recorded by other researchers.

The technology used would have been a combination of electromechanical controls, microfilm cameras and readers, all integrated into a large desk. Most of the microfilm library would have been contained within the desk, but the user could add or remove microfilm reels at will.

Vannevar Bush ( /væˈniːvɑr/ van-NEE-var; March 11, 1890 – June 28, 1974) was an American engineer, inventor and science administrator known for his work on analog computers, his role as an initiator and administrator of the Manhattan Project, as the founder of Raytheon, and for the memex, an adjustable microfilm viewer analogous to the structure of the World Wide Web. He is credited with inspiring the creation of the New Media.

For his master's thesis, Bush invented and patented a "profile tracer", a device for assisting surveyors that mapped the terrain over which it traveled. It was the first of a string of inventions. He joined the Department of Electrical Engineering at MIT in 1919, and founded the company now known as Raytheon in 1922. Starting in 1927, Bush constructed a differential analyzer, an analog computer with some digital components that could solve differential equations with as many as 18 independent variables. An offshoot of the work at MIT by Bush and others was the beginning of digital circuit design theory. Bush became Vice President of MIT and Dean of the MIT School of Engineering in 1932, and president of the Carnegie Institution of Washington in 1938.