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- Matt Machan (born 1991), Sussex cricketer
- Percival Mackey, pianist, composer and music director in the early 20th century, lived in Brighton
- Mathilde Madden, erotica author, lives in Brighton
- Sake Dean Mahomet, introduced the Turkish bath to Britain
- Stephen Mallinder, musician, lives in Brighton
- Gideon Mantell, doctor, palaeontologist, discoveror of dinosaurs (Iguanodon), lived and worked in Brighton in the 1830s
- Lesley Manville (born 1956), English actress
- Gazz Marlow Guitarist for InMe, also runs local alternative club night Guerilla Rocks
- Edward Marshall-Hall, criminal barrister famous for Edwardian theatrics in court
- Ivan Massow, entrepreneur
- Susan Maughan, singer of hit record Bobbys Girl, lived in Rottingdean
- Peter Mayle, author of A Year in Provence
- Conor Maynard, singer, was born in Brighton
- Margaret Mayo, children's author, lives in Brighton
- Pete McCarthy (1951–2004), actor and writer, lived in Brighton for a while, and a local bus was named after him
- Joe McGann, actor; star of The Upper Hand
- Kevin McNally, actor, lives in Brighton
- Neil Megson, performance artist, also known as Genesis P-Orridge
- Harriet Mellon (1777–1837), actress, wife of banker Thomas Coutts, had a house by Regency Square, Brighton
- Alan Melville, (1910–1983) revue author, playwright, lyricist, radio and TV personality moved to Brighton in 1951 and lived in Clifton Terrace and Victoria St.
- Sara Mendes da Costa, the British Telecom speaking clock
- Kevin Meredith, a.k.a. Lomokev, photographer, lives and works in Brighton
- Prince Klemens von Metternich (15 May 1773 – 11 June 1859), Austrian Foreign Minister, Diplomat and creator of the Congress of Vienna
- Max Miller, comedian, "the Cheeky Chappie", born in Brighton in 1894, lived there most of his life; blue plaque at 160 Marine Parade
- Heather Mills, ex-wife of musician and ex-Beatle Sir Paul McCartney, lives and owns the vegan restaurant VBites in Hove
- Juan, Count of Montizón, the Carlist claimant to the throne of Spain and Legitimist claimant to the throne of France — lived in Hove c.1870s – 1887, where he died; funeral mass held in Hove's Sacred Heart Church
- William Moon, teacher and inventor of an alphabet for the blind
- Gary Moore, musician, guitarist with Thin Lizzy amongst others as well as solo, lived in Hove
- Ryan Moore, three time champion jockey
- Caitlin Moran, journalist, was born in Brighton
- James Morrison, recording artist, lives in Hove
Read more about this topic: List Of People From Brighton And Hove