The PowerBook 100 was introduced on October 21, 1991, at the COMDEX computer expo in Las Vegas, Nevada. Priced at US$2,300, the PowerBook 100 was the low-end model of the first three simultaneously released PowerBooks. Its CPU and overall speed closely resembled those of its predecessor, the Macintosh Portable.

It had a Motorola 68000 processor at 16 MHz, 2-8 megabytes (MB) of RAM, a 9-inch (23 cm) monochrome backlit liquid crystal display (LCD) with 640 × 400 pixel resolution, and the System 7.0.1 operating system. It did not have a built-in floppy disk drive and was noted for its unique compact design that placed a trackball pointing device in front of the keyboard for ease of use.

Apple's then-chief executive officer (CEO) John Sculley started the PowerBook project in 1990, allocating $1 million for marketing. Despite the small marketing budget, the new PowerBook line was a success, generating over $1 billion in revenue for Apple in its first year. Sony designed and manufactured the PowerBook 100 in collaboration with the Apple Industrial Design Group, Apple's internal design team.