The Cholera basin is the established name for the western harbour basin in front of the Market Square in Helsinki, Finland.
The harbour basins were built in the early 19th century. At that time, the Market Square area consisted of the muddy Kaupunginlahti bay. Its shores had many shore huts and small piers. Where the edge of the Market Square is now was the Eteläinen Rantakatu street.
Today, the Cholera basin is the traditional site of the Finnish unscientific society's Jaakko day stone throw. Since 1995, various objects have been thrown into the basin, including an iron, a deep frozen rock, a cosmic meteorite, a wooden cobble stone, a lava rock from, half of a runestone, a rock from the Volga river and a blade sharpening stone.