The original Sony Walkman personal stereo was a transistorized miniature portable cassette tape player invented by Akio Morita, Masaru Ibuka and Kozo Ohsone in 1979, and manufactured by Sony Corporation.

Offering the ability for people to carry their own choice of music with them, the Walkman stereo was one of the most successful new consumer product introductions of the 1980s. Hit pop songs were written about it ("Wired for Sound" by Cliff Richard), hundreds of clones flooded the marketplace, and they quickly became ubiquitous amongst urban pedestrians and commuters.

The best quality Sony Walkman cassette deck was the Walkman Professional WM-D6C, which was comparable in audio quality with the best non-portable cassette decks. Unusually for a portable device, it had recording level meters and manual control of the left and right recording levels. Powered by the mains or by 4 AA batteries (compared with 2 for most Walkman models), it was widely used by journalists, and developed a following among hi-fi enthusiasts. By the late 1990s the machine was generally passed over in favor of the digital technologies of DAT and MiniDisc.

The words "Walkman", "Pressman", "Watchman", and "Discman" are trademarks of Sony, and have been applied to a wide range of portable entertainment devices manufactured by the company.

The cassette-based Walkman products are now approaching technological obsolesence as the format fades, even on the consumer market gradually being replaced by MiniDisc and solid-state MP3 players as their cost comes down. These new devices are also sometimes called "Walkman".