Abolitionism in the United Kingdom was the movement in the late 18th and early 19th centuries to end the practice of slavery, whether formal or informal, in the United Kingdom, the British Empire and the world, including ending the Atlantic slave trade. It was part of a wider abolitionism movement in Western Europe and the Americas.

The buying and selling of slaves was made illegal across the British Empire in 1807, but owning slaves was permitted until it was outlawed completely in 1833, beginning a process where from 1834 slaves became indentured "apprentices" to their former owners until emancipation was achieved for the majority by 1840 and for remaining exceptions by 1843. Former slave owners received formal compensation for their losses from the British government, known as compensated emancipation.