- William Jahn
- William James
- William Jancosko
- William Janes
- William Jarosz
- William Jefferson Black
- William Jimerson
- William Johnson
- William Johnson
- William Johnstone
- William Johnstone II
- William Jonason
- William Jones
- William Joyce
- William Kadouch-Chassaing
- William Karlson
- William Karol
- William Kasozi
- William Keesler
- William Keniry
- William Kennard
- William Kennedy
- William Kerr
- William Kessinger
- William Kidd
- William King
- William Kirshenbaum
- William Klein
- William Kloos
- William Knowles
- William Kolb
- William Komaroff
- William Kremer
- William Kridel, Jr
- William Laboratories Acquired By Temptime
- William Lafferty
- William Lapthorn
- William Lawrence
- William Lee
- William Lehun
