Bleeding Kansas, sometimes referred to as Bloody Kansas and/or the Border War, was a sequence of violent events involving abolitionists and pro-Slavery elements that took place in Kansas Territory between roughly 1854 and 1856. The territory bordered Missouri, a state where slavery was allowed, and the area became a battleground for pro-slavery and anti-slavery forces who fought over whether the resulting state of Kansas should be a slave state or a free state. There was a total of 157 deaths during this period. Historians today believe that only 56 of these deaths were connected to the issue of slavery or politics while the other 101 deaths were drunken brawls or personal issues.

A few famous people involved with Bleeding Kansas are John Brown and Silas Soule.

It has been argued by some historians that the violence during this period was the true beginning of the American Civil War.