Charles Ignatius Sancho (c. 1729 – 14 December 1780) was a British writer, composer and abolitionist. Born on a slave ship in the Atlantic Ocean, Sancho was sold into slavery in the Spanish colony of New Granada. After his parents died, Sancho's owner took the two-year-old orphan to Britain and gave him to three sisters living in Greenwich, where he remained for eighteen years. Unable to bear being a servant to them, Sancho ran away to Montagu House in Blackheath, London where John Montagu, 2nd Duke of Montagu taught him how to read and encouraged Sancho's budding interest in literature. After spending some time as a butler in the household, Sancho left and started his own business as a shopkeeper, while also starting to write and publish various essays, plays and books.

Sancho quickly became involved in the nascent British abolitionist movement, which sought to outlaw both the slave trade and the institution of slavery itself, and he became one of its most devoted supporters. Sancho's status as a property-owner meant he was legally qualified to vote in a general election, a right he exercised in 1774 and 1780, becoming the second known British African to have voted in Britain after John London. Gaining fame in Britain as "the extraordinary Negro", Sancho became, to British abolitionists, a symbol of the humanity of Africans and the immorality of the slave trade and slavery. Sancho died in 1780. The Letters of the Late Ignatius Sancho, an African, edited and published two years after his death, are the first published letter collection by a writer of African descent.

Charles Ignatius Sancho was born on a slave ship crossing the Atlantic Ocean, in what was known as the Middle Passage. His mother died not long after arriving in the Spanish colony of New Granada, which formed parts of modern-day Colombia, Ecuador, Panama, and Venezuela. He was baptised and named by the Catholic bishop of the colony. His father reportedly took his own life rather than live as a slave.

Sancho's owner took him, then barely two years old, to England and gave him to three unmarried sisters living together in Greenwich, where he lived from 1731 to 1749. The sisters gave him the surname Sancho as they believed he resembled Don Quixote's squire. The Duke of Montagu, a frequent visitor to the sisters, was impressed by Sancho's intellect, frankness, and amiability. He encouraged Sancho to read and lent him books from his personal library at Blackheath.

Sancho's informal education made his lack of freedom at Greenwich unbearable, and he ran away to Montagu House, Blackheath in 1749.

For two years until her death in 1751, Sancho worked as a butler for the Duchess of Montagu at her residence, where he immersed himself in music, poetry, reading, and writing. Upon her death in 1751, Sancho received an annuity of £30 (equivalent to £6,000 in 2025) and a year's salary.

It may have been at this time that he was freed, but the circumstances of his manumission are unknown.

On 17 December 1758 he married a West Indian woman, Anne Osborne (1733-1817), becoming a devoted husband and father. They had seven children: Frances Joanna (1761-1815), Ann Alice (1763-1805), Elizabeth Bruce (1766-1837), Jonathan William (1768-1770), Lydia (1771-1776), Katherine Margaret (1773-1779), and William Leach Osborne (1775-1810). Around the time of the birth of their third child, Sancho became a valet to George Montagu, the son-in-law of his previous patron. Sancho remained a valet until 1773.