January 2 – The discovery of a hypothetical planet Vulcan is announced at a meeting of the French Academy of Sciences in Paris, France.
January 10 – The Pemberton Mill in Lawrence, Massachusetts collapses, killing 146 workers.
January 13 – Battle of Tétouan, Morocco: Spanish troops under General Leopoldo O'Donnell, 1st Duke of Tetuan defeat the Moroccan Army.
January 20 – Camillo Benso, Count of Cavour is recalled as Prime Minister of Piedmont-Sardinia.
January 31 – Kukis raid the Chhagalnaiya plains in eastern Bengal, murdering and kidnapping hundreds of people, particularly women.
February 20 – Canadian Royal Mail steamer (1859) is wrecked on Cape Sable Island, Nova Scotia, on passage from the British Isles to the United States with all 205 onboard lost.
February 26 – White settlers massacre a band of Wiyot Indians on Indian Island, near Eureka, California. At least 60 women, children and elders are killed. Bret Harte, newspaper reporter in Arcata, reports the news to newspapers in San Francisco.
March 17 – The First Taranaki War begins at Waitara, New Zealand, when Māori refuse to sell land to British settlers.
March 22 – The Grand Duchy of Tuscany is annexed to the newly formed Kingdom of Italy.
March 24 – Sakuradamon Incident: Rōnin samurai of the Mito Domain in Japan assassinate tairō (Chief Minister) Ii Naosuke outside the Sakurada Gate of Edo Castle, disaffected with his role in the opening of Japan to foreign powers.
March–August – The second rout of the Jiangnan Daying destroys the Qing dynasty's army of 180,000.
April 2 – The first Italian Parliament meets at Turin.
April 3 – The Pony Express begins its first run from St. Joseph, Missouri, United States, to Sacramento, California, with riders carrying a small Bible.
April 4 – A new uprising erupts in Palermo.
April 9 – French typesetter Édouard-Léon Scott de Martinville creates a recording of the French folk song Au clair de la lune with his phonautograph, producing the world's earliest known intelligible sound recording of the human voice (however, it was not rediscovered until 2008).