M
- Ernst Mach — Mach number
- Karel Hynek Mácha — Máchovo jezero (Mácha's Lake), in the Czech Republic
- Niccolo Machiavelli — Machiavellian—attempting to achieve what one wants by cunning, scheming and unscrupulous methods.
- Charles Macintosh — mackintosh
- Alexander Mackenzie — Mackenzie River, Mackenzie Bay
- Colin Maclaurin - Maclaurin series, Maclaurin's inequality, Sectrix of Maclaurin, Trisectrix of Maclaurin,
- Gaius Maecenas, a Roman patron of literature and the arts, a true "maecenas"
- Ferdinand Magellan — Strait of Magellan, Large Magellanic Cloud, Small Magellanic Cloud
- François Magendie — foramen of Magendie (outlet for cerebrospinal fluid in the brain)
- Maggie, sister of Matt Groening, creator of The Simpsons — Maggie Simpson, character in The Simpsons animated TV series
- Pierre Magnol — magnolia
- Martin Mailman - American composer
- Jules Germain François Maisonneuve — Maisonneuve fracture
- Mrs. Malaprop, a character in The Rivals, a play by Richard Brinsley Sheridan - malapropism (a humorous misuse of a word)
- Thomas Malthus — Malthusian, Malthusianism, Malthusian Growth Model, Malthusian catastrophe
- Benoît Mandelbrot — Mandelbrot set
- Vinoo Mankad - Mankaded or to be run out at the bowler's end in cricket.
- Antoine Marfan — Marfan syndrome
- Marge, mother of Matt Groening, creator of The Simpsons — Marge Simpson, character in The Simpsons animated TV series
- Henrietta Maria of France, wife of Charles I — Maryland
- Queen Mariana of Austria or Marie-Anne of Austria — Mariana Islands, Mariana Trench
- Pierre Marie — Charcot-Marie-Tooth disease
- Saint Marinus — San Marino
- Benjamin Markarian — Markarian galaxies
- Michael Marks - Marks and Spencer
- Géza Maróczy — Maróczy Bind
- Marplot, the main character in Susanna Centlivre's plays The Busy Body and Marplot in Lisbon - marplot (an officious meddler or busybody who disrupts the plans of others)
- Frank Marshall — Marshall Defense
- John Marshall — Marshall Islands
- Lionel Martin — Aston Martin
- Glenn Luther Martin founded The Glenn L. Martin Company which several decades and mergers later became Lockheed Martin
- Jean Martinet — martinet; a disciplinarian
- Maurice Martenot — Ondes Martenot, an electronic musical instrument with a keyboard and slide invented in 1928.
- Mary, mother of Jesus - numerous communities and geographic features (either named St. Mary or having the word Lady in them), a large number of cathedrals, churches, and religious orders, the ladybird
- Mary the Jewess, ancient alchemist invented the Bain-marie to warm substances such as Elixir to germinate precious metals
- Maserati brothers - founders, Maserati
- Charles Mason and Jeremiah Dixon — Mason-Dixon Line
- John L. Mason — Mason jar
- Alonzo C. Mather — Mather Stock Car Company
- Harold "Matt" Matson and Elliot Handler — Mattel
- Jujiro Matsuda — founder, Mazda (also possibly inspired by Zoroastrian god Ahura Mazda)
- Queen Maud of Norway - Queen Maud Gulf (Canada), Queen Maud Land in Antarctica
- Maurice of Nassau — Mauritius
- Maussollus—mausoleum, a monumental tomb....
- Hiram Maxim — Maxim gun
- James Clerk Maxwell — maxwell, unit of magnetic flux
- Louis B. Mayer — founder of Louis B. Mayer Pictures which later merged into Metro-Goldwyn-Mayer (or MGM)
- John Loudon McAdam — macadam process of road construction, tarmac (tar+macadam) road surface
- Dick McDonald and Mac McDonald — founders, McDonald's Corporation
- James Smith McDonnell founder McDonnell Aircraft Corporation later to become McDonnell Douglas
- Giuseppe Meazza — Stadio Giuseppe Meazza, a football stadium in Italy
- Megan Kanka - Megan's Law
- Georg Meissner — Meissner's corpuscles
- Walter Meissner (and Robert Ochsenfeld) — Meissner effect (or Meissner-Ochsenfeld effect)
- Lise Meitner — meitnerium, chemical element
- Nellie Melba — Melba toast; Peach Melba; Melba, a suburb of Canberra, Australia
- Viscount Melbourne - Melbourne
- Gregor Mendel — Mendelian inheritance, Mendel Polar Station, lunar crater Mendel
- Dmitri Mendeleev — mendelevium, chemical element
- Prosper Ménière — Ménière's disease
- Mentor (Greek mythology) — mentor: a trusted friend, counselor or teacher, usually a more experienced person, mentoring programs
- Giuseppe Mercalli — Mercalli intensity scale of an earthquake
- Meirion, son of Cunedda — Merionethshire
- Franz Mesmer (1734–1815)—Mesmerism
- Robert Metcalfe — Metcalfe's law
- Methuselah — 6 litre wine bottle see Wine bottle#Sizes
- Michelangelo, Renaissance painter — Michelangelo, one of the Teenage Mutant Ninja Turtles comic characters
- Jacques Mieses — Mieses Opening
- Caspar Milquetoast — Milquetoast, "a weak, ineffectual or bland person."
- Hermann Minkowski — Minkowski addition, Minkowski inequality, Minkowski space, Minkowski diagram, Minkowski's theorem
- Ernesto Miranda — Miranda Warning
- Andrija Mohorovičić — Mohorovičić discontinuity
- Pépé le Moko fictional character from the novel and movies of the same name — Pepe Le Pew Warner Bros. French skunk character
- Vyacheslav Molotov (1890–1986) — Molotov cocktail
- James Monroe — Monroe Doctrine, Monrovia
- Monty Python's Flying Circus - Pythonesque, spam (derived from one of their sketches: Spam)
- Robert Moog — Moog synthesizer, an analog synthesizer
- Gordon Moore — Moore's Law
- Jean Moreau de Sechelles — Seychelles
- José María Morelos — Morelos
- Prince Morgan the Old of Gwent — Glamorgan
- Ernst Moro — Moro reflex
- Samuel Morse — Morse code
- John Morton (1420–1500), Chancellor of England — Morton's Fork, a choice between two equally unpleasant alternatives
- Jerry Moss and Herb Alpert — A&M Records
- Rudolf Mössbauer — Mössbauer effect
- Lord Louis Mountbatten — Mountbatten pink, naval camouflage pigment
- Wolfgang Amadeus Mozart — Mozartkugel, Mozart effect, Mozart Medal, the word 'Mozart' became synonymous for '(musical) child prodigy' and 'virtuoso'
- Erasto B. Mpemba — Mpemba effect
- Antonín Mrkos — four comets carry his name: 18D/Perrine-Mrkos, 45P/Honda-Mrkos-Pajdusakova, 124P/Mrkos and 143P/Kowal-Mrkos
- Walther Müller — Geiger-Müller tube
- David, John A. or Thomas Mulligan - Mulligan
- Baron Münchhausen — Münchausen syndrome, Münchausen syndrome by proxy
- Ian Murdock and Debra Murdock — Debian project for free software, made after combining Ian's and his wife's name Debra.
- William Lawrence Murphy — Murphy bed.
Read more about this topic: List Of Eponyms (L-Z)