|Covid-19|January 5 – Battle of Shipka Pass IV: Russian and Bulgarian forces defeat the Ottoman Empire.
January 9 – Umberto I becomes King of Italy.
January 17 – Battle of Philippopolis: Russian troops defeat the Turks.
January 23 – Benjamin Disraeli orders the British fleet to the Dardanelles.
January 24 – The revolutionary Vera Zasulich shoots at Fyodor Trepov, the Governor of Saint Petersburg.
January 28 – The Yale News becomes the first daily college newspaper in the United States.
January 31 – Turkey agrees to an armistice at Adrianople.
February 2 – Greece declares war on Turkey.
February 7 – Pope Pius IX dies after a 31½ year reign (the longest definitely confirmed).
February 8 – The British fleet enters Turkish waters and anchors off Istanbul; Russia threatens to occupy Istanbul but does not carry out the threat.
February 18 – The Lincoln County War begins in Lincoln County, New Mexico.
February 19 – The phonograph is patented by Thomas Edison.
February 20 – Pope Leo XIII succeeds Pope Pius IX as the 256th pope.
February 23 - Sadguru Shri Gajanan Maharaj appeared at Shegaon, Dist: Buldhana, Maharashtra.
February 24 – Anti-Russian demonstrations occur in Hyde Park, London.
February 28 – Mississippi State University is created by the Mississippi Legislature (under the name The Agricultural and Mechanical College of the State of Mississippi).
March 3 – The Treaty of San Stefano concludes the Russo-Turkish War; Bulgaria and Romania regain their independence from the Ottoman Empire
March 24 – The British Royal Navy frigate HMS Eurydice (1843) capsizes in the English Channel, killing all but two of the 319 crew.
March 25 – Russia rejects a British proposal to lay the San Stefano treaty before a European congress.
March 27 – In anticipation of war with Russia, Disraeli mobilizes the reserves and calls up Indian troops to Malta.
April 20 – The Stawell Gift is run for the first time in Australia.
May 2 – The Washburn "A" Mill in Minneapolis explodes, killing 18.
May 15 – The Tokyo Stock Exchange is established.
May 25 – Gilbert and Sullivan's comic opera H.M.S. Pinafore debuts in London at the Opera Comique with a first run of 571 performances.
June 1 – General Postal Union renamed Universal Postal Union (UPU).
June 4 – Cyprus Convention: The Ottoman Empire cedes Cyprus to the United Kingdom but retains the nominal title.
June 13–July 13 – The Congress of Berlin convenes to discuss the Ottoman Empire.
June 15 – Eadweard Muybridge produces the sequence of stop-motion still photographs Sallie Gardner at a Gallop in California, a predecessor of silent film demonstrating that all four feet of a galloping horse are off the ground at the same time.
June 20 – U.S. Coastal Survey renamed U.S. Coast and Geodetic Survey.
June 22 – Adolf Erik Nordenskiöld leaves Karlskrona on a voyage that will make him the first to navigate the Northern Sea Route, a shipping lane from the Atlantic Ocean to the Pacific Ocean along the Siberian coast.
July 4 – A match race between champion thoroughbred racehorses Ten Broeck and Mollie McCarty draws more than 30,000 fans to Louisville and inspires the folk song, Molly and Tenbrooks.
July 13 – The Treaty of Berlin makes Serbia, Montenegro and Romania completely independent, confirms the autonomy of Bulgaria, makes Cyprus a British possession and allows Austria-Hungary to garrison the Bosnia Vilayet.
July 26 – In California, the poet and American West outlaw calling himself "Black Bart" makes his last clean getaway when he steals a safe box from a Wells Fargo stagecoach. The empty box is found later with a taunting poem inside.
August 7 – The Salvation Army "foundation deed" is signed.
August 9 – The Wallingford Tornado of 1878, the deadliest tornado in Connecticut history, destroys the town of Wallingford, killing 34 people and injuring 70 or more.
August 26 – Uyedineniya Island is discovered in the Kara Sea by Norwegian explorer Captain Edvard Holm Johannesen.
September 3 – Over 640 die when the crowded pleasure boat Princess Alice collides with the Bywell Castle in the River Thames.
September 12 – Cleopatra's Needle is erected in London, having arrived in England on January 21.
September 20 – The Hindu, an Indian newspaper, is founded.
September 30 – The ship Priscilla arrives in Hawaii from Funchal, Madeira, marking the beginning of the Portuguese immigration to the Hawaiian Islands (1878–1913).
October 1 – Virginia Polytechnic Institute and State University (Virginia Tech) opens as Virginia Agricultural and Mechanical College in the United States.
October 14 – The world's first recorded floodlit football fixture is played at Bramall Lane in Sheffield, England.
October 17 – John A. Macdonald returns to office as Prime Minister of Canada.
October 31 – A fire destroys the Eldkvarn gristmill mill in Stockholm, Sweden.
November 17 – The first assassination attempt is made against Umberto I of Italy by anarchist Giovanni Passannante, armed with a dagger. The King survived with a slight wound in one arm. Prime minister Benedetto Cairoli blocks the aggressor, receiving a leg injury.
November 21 – The Second Anglo-Afghan War commences when the British attack Ali Masjid in the Khyber Pass.
November 26 – American-born artist James McNeill Whistler's libel case against English critic John Ruskin over a review of the painting Nocturne in Black and Gold – The Falling Rocket (in which Whistler is described as "flinging a pot of paint in the public's face") is decided in the High Court of Justice in London. Whistler wins a farthing in nominal damages and only half of the costs, leading to his bankruptcy, and alienates patrons.
December 7 — The United States territory of New Mexico is linked to the rest of the nation by railroad for the first time as the Atchison, Topeka and Santa Fe Railway inaugurates a newly completed line through the Raton Pass.
December 25 — Stella Maris Church in Sliema, Malta becomes a parish - seceding from the Parish of St. Helen's in Birkirkara.
U.S. arbitration rejects Argentine claims to Paraguay's part of the Chaco region.
Otto von Bismarck abandons his Kulturkampf and forces through legislation outlawing the Social Democrats.
10-year Nauruan Tribal War breaks out.
Yellow fever in the Mississippi Valley kills over 13,000.
The Buchan School, Isle of Man.
The Johns Hopkins University Press, America's oldest university press.
Geiger (corporation), formed as Geiger Brothers.
The following English Association football clubs:
Everton Football Club, formed as St Domingo.
Grimsby Town F.C., formed as Grimsby Pelham.
Ipswich Town Football Club, formed as amateur club Ipswich A.F.C. They will not turn professional until 1936.
Newton Heath Lancashire and Yorkshire Railway Football Club, the team that will become Manchester United.
West Bromwich Albion F.C..
Leo Tolstoy's novel Anna Karenina is published complete in book form in Moscow.
Lester Allan Pelton produces the first operational Pelton wheel.
Death of last confirmed Cape lion.
Remington, in the United States, introduce their No. 2 typewriter, the first with a shift key enabling production of lower as well as upper case characters.
A. E. Coppard, English short story writer and poet (d. 1957)
Augustus John, Welsh-born painter (d. 1961)
January 6 – Carl Sandburg, American poet and historian (d. 1967)
January 9 – John B. Watson, American psychologist (d. 1958)
January 12 – Ferenc Molnár, Hungarian-born author (d. 1952)
January 20 – Finlay Currie, Scottish actor (d. 1968)
January 22 – Constance Collier, English stage & screen actress (d. 1955)
January 23 – Rutland Boughton, English composer (d. 1960)
January 25 – Ernst Alexanderson, Swedish-born television pioneer (d. 1975)
February 1 – Milan Hodža, Slovak politician, champion of regional integration in Europe (d. 1944)
February 2 – Alfréd Hajós, Hungarian swimmer and architect (d. 1955)
February 5 – André Citroën, French automobile manufacturer (d. 1935)
February 8 – Martin Buber, Austrian philosopher (d. 1965)
February 14 – Hirota Koki, Prime Minister of Japan (d. 1948)
Giacomo "James" Colosimo, Italian-born American gangster (d. 1920)
Selim Palmgren, Finnish composer (d. 1951)
February 18 – Kate Gordon, American psychologist (d. 1963)
February 21 – The Mother (Mirra Alfassa), multi-origined spiritual leader and founder of Auroville in India (d. 1973)
February 26 – Emmy Destinn, Czech soprano (d. 1930)
February 28 – Pierre Fatou, French mathematician (d. 1929)
Egbert Van Alstyne, United States songwriter and pianist (d. 1951)
Peter D. Ouspensky, Russian philosopher (d. 1947)
Arishima Takeo, Japanese novelist, short-story writer and essayist (d. 1923)
March 5 – P. D. Ouspensky, Russian mathematician (d. 1947)
March 16 – Clemens August Graf von Galen, German Catholic cardinal (d. 1946)
March 22 – Michel Théato, Luxembourg athlete (d. 1919)
March 26 – Henry Gullett, Australian politician (d. 1940)
March 31 – Jack Johnson, American boxer (d. 1946)
April 1 – C. Ganesha Iyer, Ceylon Tamil Philologist (d. 1958)
April 4 – Stylianos Lykoudis, Greek admiral (d. 1958)
April 6 – Erich Mühsam, German author (d. 1934)
April 24 – Jean Crotti, Swiss artist (d. 1958)
Lionel Barrymore, American actor (d. 1954)
Willem Mengelberg, Dutch conductor (d. 1951)
May 3 – Jean Chiappe, French civil servant (d. 1940)
May 10 – Gustav Stresemann, Chancellor of Germany, recipient of the Nobel Peace Prize (d. 1929)
May 18 – Dr. Prescott, American doctor, explorer, and philanthropist (d. 1938)
May 21 – Glenn H. Curtiss, American aviation pioneer (d. 1930)
May 25 – Bill Robinson, African American tap dancer (d. 1949)
May 27 – Anna Cervin, Swedish artist (d. 1972)
May 28 – Paul Pelliot, French sinologist (d. 1945)
June 1 – John Masefield, English poet and novelist (d. 1967)
June 3 – Barney Oldfield, American automobile racer and pioneer (d. 1946)
June 5 – Pancho Villa, Mexican revolutionary (d. 1923)
June 12 – James Oliver Curwood, American writer and conservationist (d. 1927)
June 20 – Will Mastin, American vaudevillian (d. 1975)
June 27 – He Xiangning, Chinese revolutionary, feminist, politician, painter and poet (d. 1972)
July 3 – George M. Cohan, American singer, dancer, composer, actor, and writer (d. 1942)
July 8 - Jimmy Quinn, Scottish footballer (d. 1945)
July 10 – Otto Freundlich, German painter and sculptor (d. 1943)
Claude C. Bloch, American admiral (d. 1967)
Peeter Põld, Estonian pedagogical scientist and politician (d. 1930)
July 24 – Edward Plunkett, Baron Dunsany, Irish author (d. 1957)
August 2 – Princess Ingeborg of Denmark, Princess of Sweden (d. 1958)
August 4 – Ernest Lundeen, American lawyer and politician (d. 1940)
August 9 – Eileen Gray, Irish architect and furniture designer (d. 1976)
August 10 – Alfred Döblin, German writer (d. 1957)
August 13 – Harold Clarke Goddard, American professor and Shakespearean scholar (d. 1950)
August 19 – Manuel Luis Quezon, 2nd President of the Philippines (d.1944)
August 28 – George Whipple, American scientist, recipient of the Nobel Prize in Physiology or Medicine (d. 1976)
August 31 – Frank Jarvis, American athlete (d. 1933)
September 2 – Werner von Blomberg, German field marshal (d. 1946)
September 5 – Robert von Lieben, Austrian physicist (d. 1913)
September 9 – Sergio Osmena, 4th President of the Philippines (d. 1961)
September 13 – Matilde Moisant, American pilot (d. 1964)
September 14 – Ion Farris, American politician, former Speaker of the Florida House of Representatives (d. 1934)
September 18 – James O. Richardson, American admiral (d. 1974)
September 20 – Upton Sinclair, American writer (d. 1968)
September 22 – Yoshida Shigeru, Prime Minister of Japan (d. 1967)
September 24 – C. F. Ramuz, Swiss writer (d. 1947)
October 1 – Othmar Spann, Austrian philosopher and economist (d. 1950)
October 9 – Robert Warwick, American stage & screen actor (d. 1964)
October 16 – Maxie Long, American athlete (d. 1959)
October 29 – Alexander von Falkenhausen, German general (d. 1966)
November 1 – Carlos Saavedra Lamas, Argentine politician, recipient of the Nobel Peace Prize (d. 1959)
Inigo Campioni, Italian admiral (d. 1944)
Julie Manet, French painter (d. 1966)
Leopold Staff, Polish poet (d. 1957)
November 17 – Grace Abbott, American social worker and activist (d. 1939)
Ernest Joseph King, Commander in Chief, United States Fleet and Chief of Naval Operations (COMINCH-CNO) during World War II (d. 1956)
Frank Pick, British transport administrator and designer (d. 1941)
December 1 – Nathaniel Baldwin, American inventor and a supporter of the early Mormon fundamentalist movement (d. 1961)
December 10 – C. Rajagopalachari, Indian politician and freedom-fighter. (d. 1972)
December 18 – Joseph Stalin, leader of the Soviet Union (d. 1953)
Louis Chevrolet, Swiss-born race driver and automobile builder (d. 1941)
Joseph Schenck, Russian-born American film executive (d. 1961)
December 28 – Nikolai Bryukhanov, Soviet statesman and political figure who served as People's Commissar of Finances (d. 1938)
Elizabeth Arden, Canadian-born beautician and cosmetics entrepreneur (d. 1966)
Horacio Quiroga, Argentine writer (d. 1937)
January 8 – Nikolay Nekrasov, Russian poet (b. 1821)
January 9 – King Victor Emmanuel II of Italy (b. 1820)
January 18 – Antoine César Becquerel, French scientist (b. 1788)
February 7 – Pope Pius IX (b. 1792)
February 11 – Gideon Welles, American politician (b. 1802)
February 19 – Charles-François Daubigny, French painter (b. 1817)
February 26 – Angelo Secchi, Italian astronomer (b. 1818)
March 8 – Archduke Franz Karl of Austria (b. 1802)
March 20 – Julius von Mayer, German physician and physicist and one of the founders of thermodynamics (b. 1814)
March 27 – George Gilbert Scott, British architect (b. 1811)
April 8 – Henrietta Treffz, soprano, first wife of Johann Strauss II (b. 1818)
April 11 – Robert Wentworth Little, British occultist (b. 1840)
April 12 – William M. Tweed, American politician (b. 1823)
April 25 – Anna Sewell, English author (b. 1820)
May 12 – Anselme Payen, French chemist (b. 1795)
May 13 – Joseph Henry, American scientist (b. 1797)
May 14 – Ōkubo Toshimichi, Japanese samurai and later leader of the Meiji restoration (b. 1830)
May 28 – John Russell, 1st Earl Russell, Prime Minister of the United Kingdom (b. 1792)
Robert Stirling, Scottish clergyman and inventor (b. 1790)
Achille Baraguey d'Hilliers, Marshal of France (b. 1795)
Porter Rockwell, Mormon bodyguard (b. 1815)
George V of Hanover (b. 1819)
Hendrik Jut, Dutch murderer (b. 1851)
June 27 – Sidney Breese, U.S. senator from Illinois known as the "father of the Illinois Central Railroad" (b. 1800)
July 1 – Catherine Winkworth, English translator of hymns (b. 1827)
July 17 – Aleardo Aleardi, Italian poet (b. 1812)
July 23 – Carl Freiherr von Rokitansky, Bohemian pathologist, philosopher and politician (b. 1804)
August 13 – Henry James Montague, English-born actor (b. 1844)
August 16 – Richard Upjohn, English-American architect (b. 1802)
August 26 – Mariam Baouardy, Syrian Melkite Greek Catholic nun, canonized (b. 1846)
August 30 – James Geiss, English businessman (b. 1820)
September 7 – Mehmed Ali Pasha, Prussian-born Ottoman military leader (b. 1827)
October 20 – Hiram Paulding, American admiral (b. 1797)
November 20 – William Thomas (Islwyn), Welsh poet (b. 1832)
November 28 – Orson Hyde, American religious leader (b. 1805)
December 10 – Henry Wells, American businessman (b. 1805)
December 14 – Princess Alice, Grand Duchess of Hesse and by Rhine (b. 1843)
December 25 – Henry K. Hoff, American admiral (b. 1809)
The Doctor Who novel Imperial Moon takes place in this year.
1878 (MDCCCLXXVIII) was a common year starting on Tuesday (dominical letter F) of the Gregorian calendar and a common year starting on Sunday (dominical letter A) of the Julian calendar, the 1878th year of the Common Era (CE) and Anno Domini (AD) designations, the 878th year of the 2nd millennium, the 78th year of the 19th century, and the 9th year of the 1870s decade. As of the start of 1878, the Gregorian calendar was 12 days ahead of the Julian calendar, which remained in localized use until 1923.