- Apr 4 Comte de Lautréamont, French writer (Les Chants de Maldoror), born in Montevideo, Uruguay (d. 1870)
- Apr 4 Raoul Pictet, Swiss physicist who invented liquid nitrogen and was a pioneer of cryogenics, born in Geneva, Switzerland (d. 1929)
- Apr 26 Giuseppe Arimondi, Italian general who fought in the Italo-Ethiopian War, born in Savigliano (d. 1896)
- Apr 28 Johann Oskar Backlund, Swedish-Russian astronomer (planets/asteroids), born in Länghem, Sweden (d. 1916)
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