Douglas Carl Engelbart (January 30, 1925 – July 2, 2013) was an American engineer and inventor, and an early computer and Internet pioneer. He is best known for his work on founding the field of human–computer interaction, particularly while at his Augmentation Research Center Lab in SRI International, which resulted in creation of the computer mouse, and the development of hypertext, networked computers, and precursors to graphical user interfaces. These were demonstrated at The Mother of All Demos in 1968. Engelbart's law, the observation that the intrinsic rate of human performance is exponential, is named after him.

NLS, the "oN-Line System," developed by the Augmentation Research Center under Engelbart's guidance with funding primarily from ARPA (as DARPA was then known), demonstrated numerous technologies, most of which are now in widespread use; it included the computer mouse, bitmapped screens, hypertext; all of which were displayed at "The Mother of All Demos" in 1968. The lab was transferred from SRI to Tymshare in the late 1970s, which was acquired by McDonnell Douglas in 1984, and NLS was renamed Augment (now the Doug Engelbart Institute). At both Tymshare and McDonnell Douglas, Engelbart was limited by a lack of interest in his ideas and funding to pursue them and retired in 1986.

In 1988, Engelbart and his daughter Christina launched the Bootstrap Institute – later known as The Doug Engelbart Institute – to promote his vision, especially at Stanford University; this effort did result in some DARPA funding to modernize the user interface of Augment. In December 2000, United States President Bill Clinton awarded Engelbart the National Medal of Technology, the U.S.'s highest technology award. In December 2008, Engelbart was honored by SRI at the 40th anniversary of the "Mother of All Demos".