- Gender: Male
- Birthday: 1862-09-11
- Day of Death: 1910-06-05 ( 48 years old )
- Place of Birth: Greensboro, North Carolina, USA
- Also Known As: William Sydney Porter / Olivier Henry / О. Генри / Уильям Сидни Портер / James L. Bliss / O. Henry / O'Henry
William Sydney Porter (September 11, 1862 – June 5, 1910), known by his pen name O. Henry, was an American short story writer. His stories are known for their surprise endings.