Dr. Douglas C. Engelbart is best known for inventing the computer mouse (in a joint effort with Bill English); as a pioneer of human-computer interaction whose team developed hypertext, networked computers, and precursors to GUIs.

Engelbart was the primary force behind the design and development of the On-Line System, or NLS. He and his team at the Augmentation Research Center (the lab he founded) developed computer-interface elements such as bit-mapped screens, multiple windows, groupware, hypertext and precursors to the graphical user interface. He conceived and developed many of his user interface ideas back in the mid-1960s, long before the personal computer revolution, at a time when most individuals were kept away from computers, and could only use computers through intermediaries (see batch processing), and when software tended to be written for vertical applications in proprietary systems.

In 1970 Engelbart received a patent for the wooden shell with two metal wheels (computer mouse U.S. Patent 3,541,541), describing it in the patent application as an "X-Y position indicator for a display system". Engelbart later revealed that it was nicknamed the mouse because the tail came out the end. It was also called the bug at the time but eventually this practice died out.

He never received any royalties for his mouse invention, partly because his patent expired in 1987, before the personal computer revolution made the mouse an indispensable input device, and also because subsequent mice used different mechanisms that did not infringe upon the original patent. During an interview, he says "SRI patented the mouse, but they really had no idea of its value. Some years later I learned that they had licensed it to Apple for something like $40,000."

Because Engelbart's research and tool-development for online collaboration and interactive human-computer interfaces was partially funded by ARPA, he became involved with the, ARPANET (the precursor of the Internet).

On October 29, 1969, the world's first electronic computer network, the ARPANET, was established between nodes at Leonard Kleinrock's lab and Engelbart's lab. Interface Message Processors at both sites served as the backbone of the first Internet.

Currently (at age 80 in 2005), he is the director of his own company, the Bootstrap Institute which he founded in 1988 with his daughter, Christina Engelbart. It is located in Fremont, California and promotes Engelbart's latest refinement of his philosophy, the concept of Collective IQ, and development of what he calls Open Hyper-Document Systems(OHS), and HyperScope, a subset of OHS.