There's some question about what makes a laptop, a laptop. Is it just about size? Ease of portability? Or do things like a rechargeable battery or screen size make a difference? Which one qualifies as "first" in the flurry of IBM competitors in the early 1980s is a difficult one, too.
The Osborne 1 sometimes gets the distinction of being the first commercially successful portable computer. Released in 1981, it weighed 23.5 pounds -- easier to tote than the IBM 5100, but still not something you'd actually carry in your lap. And since it had no power supply (there was an optional battery pack that would give you an hour of use), it couldn't be used just anywhere. The Osborne 1 had 64K RAM, dual floppy disk drives, and a five-inch screen. It came with lots of software, worth almost as much as the machine itself. The whole thing closed up (it had a fold-down keyboard) and Osborne pointed out that it could fit under an airline seat. Retailing at $1795, it was a vast improvement over previous versions. But it's called a "luggable" computer today -- it's definitely not a laptop.
The first laptop actually could fit in your lap. And it has an unexpected feature: a tiny, dot-matrix printer that used adding machine tape. Announced by Epson in 1981 and produced a few years later, the HX-20 was small enough to easily carry around at 3.5 pounds. It also had four rechargeable batteries. The display was much smaller than the Osbourne 1's; it could display just four lines of 20 characters. The data-storage device was a mini cassette recorder, and the computer came with either 16K or 32K of RAM. The HX-20 came in a hard case and cost around $795. A review written by David Ahl in Creative Computing magazine (published in March 1983) includes this: "For working on a plane, train or away from the office, the HX-20 is unrivaled. How often I have dreamed of having a spreadsheet or word processing computer with me on cross country or transatlantic plane trips! It would seem that the HX-20 is the answer to these dreams" [source: Creative Computing].
It still didn't look like a laptop. The flip-form design came a bit later, and then the first machine to be marketed using the word "laptop" came out in spring 1983. But the HX-20 was arguably the first portable computer that you could easily carry and use anywhere.