The famous British abolitionist known for his work against slavery was William Wilberforce. A prominent member of the British Parliament, Wilberforce dedicated much of his political career to the abolitionist movement. He played a crucial role in passing the Abolition of the Slave Trade Act in 1807, which made it illegal to engage in the slave trade within the British Empire. Wilberforce's relentless advocacy and moral conviction influenced public opinion and contributed to the eventual emancipation of enslaved people in the British colonies in 1833.