In the year AD
- The tide in the Greek War of Independence turns against the Ottoman Empire. The Ottomans capture Athens, but the bickering Greek political factions finally get their act together, setting aside their bitter rivalries to elect Capo d’Istria president of Greece. To make matters worse, the great European powers enter into the fray on the side of the Greeks due to romantic feelings of attachment to the "Cradle of Western Civilization" and pathos of Lord Byron's death. In the Treaty of London, Britain, France, and Russia demand that the Ottomans cease attacking the Greeks. When Ottoman operations continue, a combined British, French, and Russian fleet destroys the much larger larger but inferior Turkish-Egyptian Fleet at the Battle of Navarino, in what would eventually turn out to be a death blow to Ottoman hopes of keeping Greece.
- A combined Argentine-Uruguayan force under Carlos María de Alvear decisively defeats the Brazilians at the Battle of Ituzaingó, paving the way for the creation of an independent nation of Uruguay.
- The Siamese-Laotian War continues in Southeast Asia. Things are going badly for the Lao Kingdom, as the Siamese drive them back into Laos, defeating them in the bloody seven-day Battle of Nong-Bua-Lamphu and sacking their capital at Vientiane.
- American prophet Joseph Smith claims that on Mount Cumorah near Palmyra, New York the angel Maroni revealed to him the Golden Plates from which he would later translate the Book of Mormon and establish the Church of Jesus Christ of Latter-day Saints (Mormons).
- In an effort to establish their dominion over their lands, the Cherokee establish a democratic Cherokee Nation, with its capital at New Echota in northern Georgia, under a constitution providing for a democratically elected head chief, a senate, and a house of representatives.
- The first-ever New Orleans Mardi Gras celebration is initiated by a group of students back from school in France.
- The state of New York bans slavery.
- French chemist Joseph Nicephore Niepce takes the first true photograph.
- Scottish botanist Robert Brown discovers what will later become known as Brownian motion by observing the movement of plant spores floating in water.
- Swedish chemist J.J. Berzelius first recognizes isomerism.
- English chemist John Walker invents strike anywhere matches.
- The Baltimore and Ohio Railroad is chartered, and will become the first public railroad in the United States.
- Edgar Allen Poe publishes his first book, Tamerlane and Other Poems.
- Chinese novelist Li Ruzhen completes his wildly popular fantasy novel, Flowers in the Mirror.
- The first African-American newspaper, Freedom's Journal is published in New York by John Russworm and Samuel Cornish.
- The University of Toronto is founded as "King's College."
These people were born in 1827:
These people died in 1827:
1826 - 1827 - 1828