Walkman is an audio cassette player used to market its portable audio and video players. The original Walkman introduced a change in music listening habits, allowing people to carry their own choice of music with them. The original Walkman was marketed in 1979 as the Walkman in Japan, the Soundabout in many other countries including the US, Freestyle in Sweden and the Stowaway in the UK. The device was built in 1978 by audio division engineer Nobutoshi Kihara for Sony co-chairman Morita, who wanted to be able to listen to operas during his frequent transpacific plane trips. Morita hated the name "Walkman" and asked it to be changed, but relented after being told by junior executives that a promotion campaign had already begun using the 'Walkman' name and would be too expensive to change.

A device called the Stereobelt, had been invented by the German-Brazilian Andreas Pavel International Herald Tribune: Portable stereo's creator got his due, eventually] and patented in the U.S. in 1978. After lengthy legal battles, Andreas Pavel was paid by Sony.

However, the original patent for a personal stereo was registered by Balram Shotam (BAAL). The patent was filed in the U.K in 1974. Baal had a prototype built in 1972 while he was in the record industry as President of BAAL Records distributing ABC and AVCO (Stylistics) Records. He used his prototype extensively while travelling on airplanes between local studios in Belgium and Abbey Road studios in London when he was producing and audio-engineering the October Cherries Dreamseller album for EMI in Belgium. The patent number in the UK is #2064326. This was the first wearable electronic entertainment device ever patented and a copy of the patent was sent to Akio Morita of Sony including copies to Matsushita in Japan in 1976. The patent was for a transportable cassette player which did not allow recording and was solely connected to headphones.

The names "Walkman", "Pressman", "Watchman", "Scoopman", "Discman", and "Talkman" are trademarks of Sony, and have been applied to a wide range of portable entertainment devices manufactured by the company. Sony continues to use the "Walkman" brand name for most of their portable audio devices, after the "Discman" name for CD players was dropped in the late 1990s. According to Sony, the plural form is "Walkman Personal Stereos", rather than "Walkmans" or "Walkmen" (presumably to preserve their trademark on "Walkman").

In March 2007, Sony extended the Video Walkman brand by launching its first digital, flash-based video Walkman, the A800 series, where A stands for "All in one", "Advanced", and "Attractive".