1861

• January 1 - Benito Juarez captures Mexico City
• January 2 - Friedrich Wilhelm IV of Prussia dies and is succeeded by Wilhelm I
• January 3 - American Civil War: Delaware votes not to secede from the United States
• January 9 - Mississippi becomes the second state to secede from the Union, preceding the American Civil War.
• January 10 - Florida secedes from the United States
• January 11 - Alabama secedes from the United States
• January 14 - Mehmed VI, future Ottoman sultan.
• January 18 - Georgia joins the Confederacy
• January 21 - American Civil War: Jefferson Davis resigns from the United States Senate
• January 26 - American Civil War: Louisiana secedes from the Union.
• January 29 - Kansas is admitted as the 34th U.S. state.
• February 1 - American Civil War: Texas secedes from the United States.
• February 4 - American Civil War: In Montgomery, Alabama the Confederate States of America is formed by delegates from six break-away United States.
• February 8 - American Civil War: The Confederate States of America are formed.
• February 9 - American Civil War: Jefferson Davis is elected the Provisional President of the Confederate States of America by the Confederate convention at Montgomery, Alabama.
• February 11 - American Civil War: US House unanimously passes resolution guaranteeing non-interference with slavery in any state.
• February 18 - In Montgomery, Alabama Jefferson Davis is inaugurated as the first and only President of the Confederate States of America.
• February 18 - Victor Emmanuel of Savoy becomes King of Italy
• February 19 - Serfdom is abolished in Russia.
• February 23 - President-elect Abraham Lincoln arrives secretly in Washington, DC after an assassination attempt in Baltimore, Maryland.
• February 27 - A crowd in Warsaw protesting Russian rule over Poland is fired upon by Russian troops killing five protesters.
• February 28 - Colorado is organized as a United States territory.
• March 2 - Nevada is organized as a United States territory.
• March 4 - Abraham Lincoln succeeds James Buchanan as President of the United States.

• March 11 - The Constitution of the Confederate States of America is adopted.
• March 17 - Proclamation of the kingdom of Italy.
• March 19 - First Taranaki War ends in New Zealand
• April 12 - United States Civil War begins at Fort Sumter, South Carolina
• April 27 - President Abraham Lincoln suspends the writ of habeas corpus in the United States.
• April 27 - American Civil War: West Virginia secedes from Virginia.
• May 6 - American Civil War: Arkansas secedes from the Union.
• May 7 - American Civil War: Tennessee secedes from the Union.
• May 8 - American Civil War: Richmond, Virginia is named the capital of the Confederate States of America.
• May 13 - American Civil War: Victoria of the United Kingdom issues a "proclamation of neutrality" which recognizes the breakaway states as having belligerent rights.
• May 20 - American Civil War: Kentucky proclaims its neutrality which will last until September 3 when Confederate forces enter the state. North Carolina secedes from the United States
• July 21 - American Civil War: First Battle of Bull Run - At Manassas Junction, Virginia, the first major battle of the war begins (Confederate victory).
• July 25 - American Civil War: The Crittenden-Johnson Resolution is passed by the United States Congress stating that the war is being fought to preserve the Union and not to end slavery.
• July 26 - American Civil War: George McClellan assumes command of the Army of the Potomac following a disastrous Union defeat at the First Battle of Bull Run.
• August 5 - American Civil War: In order to help pay for the war effort, the United States government issues the first income tax as part of the Revenue Act of 1861 (3% of all incomes over US $800; rescinded in 1872).
• September 3 - American Civil War: Confederate General Leonidas Polk invades neutral Kentucky, prompting the state legislature to ask for Union assistance.
• September 6 - American Civil War: Forces under Union General Ulysses S. Grant bloodlessly capture Paducah, Kentucky, which gives the Union control the mouth of the Tennessee River.
• October 21 - American Civil War: Battle of Ball's Bluff - Union forces under Colonel Edward Baker are defeated by Confederate troops in the second major battle of the war. Baker, a close friend of Abraham Lincoln, is killed in the fighting.
• October 31 - American Civil War: Citing failing health, Union General Winfield Scott resigns as Commander of the United States Army.
• November 1 - American Civil War: US President Abraham Lincoln appoints George McClellan as commander of the Union Army, replacing the aged General Winfield Scott.
• November 2 - American Civil War: Western Department Union General John C. Fremont is relieved of command and replaced by David Hunter.
• November 6 - American Civil War: Jefferson Davis is elected president of the Confederate States of America.
• November 7 - American Civil War: Battle of Belmont - In Belmont, Missouri, Union forces led by General Ulysses S. Grant overrun a Confederate camp but are forced to retreat when Confederate reinforcements arrive.
• November 8 - American Civil War: The "Trent Affair" - The USS San Jacinto stops the United Kingdom mail ship Trent and arrests two Confederate envoys, James Mason and John Slidell, sparking a diplomatic crisis between the UK and US.
• November 21 - American Civil War: Confederate President Jefferson Davis appoints Judah Benjamin secretary of war.
• Kansas becomes 34th state in the United States

• Victor Emmanuel becomes first king of Italy
• Change of emperor of the Ottoman Empire from Abd-ul-Mejid (1839-1861) to Abd-ul-Aziz (1861-1876)
• Sir William Crookes discovers Thallium (see Discovery of the chemical elements)
• Ioan Kasatkin landed on Hakodate and introduced the Eastern Orthodox into Japan.

• 1861 in literature
• 1861 in science
• 1861 in music

• January 14 - Sultan Mehmed VI of the Ottoman Empire (+ 1926)
• February 12 - Lou Andreas-Salome, author (+ 1937)
• February 26 - King Ferdinand of Bulgaria (+ 1948)
• February 27 - Rudolf Steiner, anthroposoph (+ 1925)
• April 8 - Son, Byong-Hi, one of the leaders of the Samil, or March 1st Movement in Korea
• April 15 - Bliss Carman, poet
• May 6 - Rabindranath Tagore
• October 16 - J. B. Bury
• October 30 - Antoine Bourdelle, sculptor
• November 6 - James Naismith, inventor of basketball
• December 8 - Georges Méliès , French film director, allegedly the first.
• December 16 - Antonio de La Gandara, painter
• December 20 - Ivana Kobilca, Slovene painter (+ 1926)

• January 2 - Friedrich Wilhelm IV, king of Prussia
• January 17 - Lola Montez (adventurer)
• June 25 - Abd-ul-Mejid, Ottoman sultan
• July 25 - Jonas Furrer, Swiss Federal Councilor
• December 14 - Prince Albert of Saxe-Coburg-Gotha, Prince Consort, husband of Queen Victoria

• China -
• Xianfeng Emperor of China, Qing Dynasty (1850-1861)
• Tóngzhì Emperor of China, Qing Dynasty (1861-1875)
• Denmark - Frederick VII, King of Denmark (1848-1863)
• France - Napoleon III, Emperor of France (1852-1870)
• Norway - Charles IV, King of Sweden and Norway (1859-1872)
• Ottoman Empire -
• Abd-ul-Mejid, Sultan of the Ottoman Empire (July 2, 1839 to June 25, 1861)
• Abd-ul-Aziz, Sultan of the Ottoman Empire (1861-1876)
• Prussia -
• Frederick William IV, King of Prussia (1840-1861)
• Wilhelm I, King of Prussia (1861-1871)
• Russia - Alexander II, Tsar of Russia (1855-1881)
• Spain - Isabella II, Queen of Spain (September 29, 1833 to September, 1868)
• United States -
• James Buchanan, President of the United States (1857-1861)
• Abraham Lincoln, President of the United States (1861-1865)