When was the world's first laptop computer introduced in the market and by whom?

The Epson HX-20 (also known as the HC-20) was the first laptop computer. It was invented in July 1980 by Yukio Yokozawa, who worked for Suwa Seikosha, a branch of Japanese company Seiko (now Seiko Epson), receiving a patent for the invention. It was announced in 1981 as the HC-20 in Japan, and was introduced by Epson in North America as the HX-20 in 1981, at the COMDEX computer show in Las Vegas, where it drew significant attention for its portability.
Source: epson.com