Thaddeus Liu was a 19th-century Chinese Catholic priest and martyr who served in the Sichuan and Guizhou provinces. Born in 1773 in Qionglai, he was raised in poverty by his mother following his father's early death. After working as a priest's assistant and studying Latin, he was ordained at age 34. His religious service ended when he was arrested by authorities in 1821, leading to his imprisonment, torture, and eventual execution by strangulation in 1823.