Flein (help·info) is a municipality in the district of Heilbronn in Baden-Württemberg in southern Germany.

The communal land of Flein already was settled during the linear pottery culture of the neolithic. The village was first mentioned in 1188 within an imperial document as Flina. The name presumably comes from the Old High German term flins respectively the Middle High German vlins, meaning something like "pebble" or "hard stone".

In 1385 the free imperial city Heilbronn bought the village from the Lords of Sturmfeder. During the German Peasants' War many insurgent farmers of the region assembled in Flein around of their head Jäcklein Rohrbach. Like most of Germany, Flein suffered great damage during the Thirty Years' War.

In 1802 Flein became part of Württemberg. The enormous increase of population after World War II is due to the settlement of many refugees and creation of building land a few years later. In the 1970s the population of Flein voted against an incorporation to Heilbronn and for combining a joint association of administrations with Talheim.