- William Kroll
- William Kuhlman
- William Kunsman
- William Kunstler
- William Kurk
- William Lang
- William Larsen
- William Larsen
- William Larson
- William LaVant
- William Lawes
- William Lawford
- William Lawrence
- William Lazarus
- William Le Massena
- William Leal
- William LeBaron
- William Lee
- William Lee Ellis
- William Lee Self
- William Lesser
- William Levi Dawson
- William Lewarne Harris
- William Lewis
- William Lincoln
- William Linton
- William Lipke
- William Llerena
- William Lloyd Webber
- William Long
- William Loose
- William Lorin
- William Loughborough
- William Lovelock
- William Lowman
- William Lucas
- William Ludwig
- William Luna
- William Maag
- William MacGregor
- William Mack
- William Maestre
- William Magalhães
- William Maher
- William Mallory
- William Mapulanga
- William March
- William Marshall
- William Marshall
- William Marshall
- William Martel
- William Mason
- William Matheson
- William Mathias
- William Mathias
- William Matteuzzi
- William Matteuzzi [Tenor]
- William Matthews
- William Maxwell
- William Maxwell
- William Mayer
- William Mays
- William McAlpine
- William McCallum
- William McCauley
- William McCoy
- William McDowell
- William McGee
- William McLean
- William McMullen
- William McNally
- William Menefield
- William Mennefield