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- Mike Lally ("To Serve Man" (uncredited), ("The Silence") (uncredited), and "The Big Tall Wish" (uncredited))
- Gil Lamb ("Once Upon a Time"
- Douglas Lambert ("The Self-Improvement of Salvadore Ross")
- Paul Lambert (actor) ("King Nine Will Not Return")
- Martin Landau ("Mr. Denton on Doomsday" and "The Jeopardy Room")
- Muriel Landers ("A Piano in the House")
- Charles Lane ("Mr. Bevis")
- Rusty Lane ("The Mighty Casey")
- Paul Langton ("Where Is Everybody?" and "On Thursday We Leave for Home")
- William Lanteau ("The Bard")
- Robert Lansing ("The Long Morrow")
- John Larch ("Perchance to Dream", "Dust" and "It's a Good Life")
- Mary La Roche ("A World of His Own" and "Living Doll")
- Anker Larsen ("An Occurrence at Owl Creek Bridge")
- Henry Lascoe ("The Bard")
- John Lasell ("Back There")
- Wesley Lau ("The Fugitive" and "Twenty Two")
- S. John Launer ("Third from the Sun") (Voice only) (uncredited), "In Praise of Pip" (uncredited), "The Purple Testament", "And When the Sky Was Opened" (uncredited))
- Frederic Ledebur ("The Howling Man")
- Norman Leavitt ("Mr. Garrity and the Graves")
- Cloris Leachman ("It's a Good Life")
- Ruta Lee ("A Short Drink From a Certain Fountain")
- Art Lewis ("The Fever" and "A Most Unusual Camera" (uncredited))
- Derrik Lewis ("The Thirty-Fathom Grave")
- Robert P. Lieb ("The Night of the Meek")
- George Lindsey ("I Am the Night—Color Me Black")
- Joanne Linville ("The Passersby")
- Josie Lloyd ("The Old Man in the Cave")
- Suzanne Lloyd ("Perchance to Dream")
- Felix Locher ("The Silence")
- Frank London ("A Penny for Your Thoughts" and "Steel")
- Richard Long ("Person or Persons Unknown" and "Number 12 Looks Just Like You")
- Jon Lormer ("Dust", "Execution, "The Last Rites of Jeff Myrtlebank" and "Jess-Belle")
- Donald Losby ("Mr. Dingle, the Strong")
- Phyllis Love ("Four O'Clock")
- Celia Lovsky ("Queen of the Nile")
- Tom Lowell ("The Changing of the Guard")
- Ida Lupino ("The Sixteen-Millimeter Shrine")
- Richard Lupino ("King Nine Will Not Return") (uncredited)
- Allan Lurie ("Escape Clause") (uncredited)
- Jimmy Lydon ("Back There")
- Ken Lynch ("Mr. Denton on Doomsday")
- Denise Lynn ("Stopover in a Quiet Town") (uncredited)
- Therese Lyon ("Mirror Image") (as Terese Lyon)
- Gene Lyons ("King Nine Will Not Return")
- Herbert Lytton ("What's in the Box")
Read more about this topic: List Of The Twilight Zone (1959 TV Series) Guest Stars