Mason Lamar Williams III (January 20, 1943 – June 28, 2021) was an engineer and physicist, noted for his contributions in the areas of magnetic recording and data storage on hard disk drives (HDD).

Williams represented IBM on the National Storage Industry Consortium (INSIC) UltraHigh Density Magnetic Recording Head project.

Williams worked for Hitachi Global Storage Technologies (HGST) and continued to conduct fundamental research and modeling of magnetic recording physics and on HDD system integration.

After Williams retired from Hitachi GST in 2005, he played a major role in the restoration of the IBM RAMAC, the first commercial hard disk drive.

[5][7][8] In 1999, Williams was elevated to the grade of IEEE Fellow for "contributions to the understanding of the digital magnetic recording process and the continued progress of areal density of disk drives".

He gave a presentation entitled "Beyond the Limits of Magnetic Recording: An Itinerant Magnetician Looks at Hysterical Loops"[2] at multiple locations throughout Europe, Asia, and America.