- Jan 1 Emancipation Proclamation issued by Abraham Lincoln to free slaves in US confederate states
- Mar 19 Confederate cruiser SS Georgiana destroyed on her maiden voyage with a cargo of munitions, and medicines then valued over $1,000,000. Wreck discovered exactly 102 years later by teenage diver and pioneer underwater archaeologist E. Lee Spence.
- Apr 21 Bahá'u'lláh, founder of the Bahá'í Faith, enters garden of Rivden near Baghdad. He makes his declaration as a Messenger of God during the 12 days spent there
- Jul 1 Battle of Gettysburg, Pennsylvania; Lee's northward advance halted
- Jul 3 Battle of Gettysburg, largest battle ever fought on the American continent, ends in a major victory for the Union during the US Civil War
- Jul 12 In New Zealand, British forces invade Waikato, home of the Maori King Movement, beginning a new phase of the wars between Maori and Colonial British
- Jul 30 Indian Wars: Chief Pocatello of the Shoshone tribe signs the Treaty of Box Elder, promising to stop harassing the emigrant trails in southern Idaho and northern Utah
- Oct 26 International conference begins in Geneva aimed at improving medical conditions on battlefields - beginning of the Red Cross
- Nov 19 US President Abraham Lincoln delivers his Gettysburg address beginning; "Four score & seven years ago..."
- Dec 8 Abraham Lincoln issues his Amnesty Proclamation and plan for Reconstruction of the South
- Oct 26 Football Association forms in England, standardizing soccer, splitting with rugby
Patent granted for a process of making color photographs
On November 23, 1863