Louis Silvie Zamperini (January 26, 1917 – July 2, 2014) was an American World War II veteran, Olympic distance runner, and Christian evangelist. He began running in high school and qualified for the United States in the 5,000 m event at the 1936 Summer Olympics, where he finished eighth and set a new lap record.

Zamperini was commissioned in the United States Army Air Forces as a lieutenant. He served as a bombardier on B-24 Liberators in the Pacific. On a search and rescue mission, his plane experienced mechanical difficulties and crashed into the ocean. After drifting at sea on a life raft for 47 days, with two other crewmates, Zamperini landed on the then Japanese Marshall Islands and was captured.

He was taken to a total of four different prisoner-of-war camps in Japan, where he was tortured and beaten by Japanese military personnel—including Mutsuhiro Watanabe—because of Zamperini's status as a famous Olympic runner. He was later taken to a new prison camp at a coal factory, and after much hardship, he was finally released. Following the war he initially struggled to overcome his ordeal, afflicted with post-traumatic stress disorder and alcoholism.

He later became a Christian evangelist with a strong belief in forgiveness. From 1952 onwards, he devoted himself to at-risk youth. Zamperini is the subject of three biographical films: Unbroken (2014), its sequel Unbroken: Path to Redemption (2018), and Captured by Grace (2015).

Louis Zamperini was born on January 26, 1917, in Olean, New York, to Anthony Zamperini (1889-1975) and Louise Dossi (1898-1993), both native to Verona in northern Italy. He had an older brother named Pete (1915-2008) and two younger sisters, Sylvia (1918-2008) and Virginia (1923-2008). He was raised in a strict, devout Catholic household. Regardless, he took up smoking at age 5 and drinking at age 8. He struggled with bullies and supposedly almost died twice, once due to a house fire, and another from having fallen into an oil rig, almost drowning. In later childhood, his brother Pete was highly supportive of him and encouraged him to start his running career.

The Zamperini family moved from Olean, New York to Long Beach, California when Louis Zamperini was two years old. In 1919, the family moved to nearby Torrance where Louis attended Torrance High School. He and his family spoke no English when they moved to California, making him a target for bullies because of his Italian roots. His father taught him how to box in self-defense. Soon he claimed to be "beating the tar out of every one of them; but I was so good at it that I started relishing the idea of getting even. I was sort of addicted to it."

To stop Zamperini from getting into trouble, his older brother Pete got him involved in the school track team, where Pete was already a star. Before then, in the ninth grade, Zamperini's classmates challenged him to a footrace. Louis came in last, and was humiliated. Pete took Louis on several training runs. Zamperini began winning races, and he was becoming much faster. After Louis found his role model, Glenn Cunningham, he took up distance running. At the end of his freshman year, he finished fifth in the All City C-division 660 yards (600 m) dash.

It was the recognition, nobody in school, except for a few of my buddies, knew my name before I started running. Then, as I started winning races, other kids called me by name. Pete told me I had to quit drinking and smoking if I wanted to do well, and that I had to run, run, run. I decided that summer to go all-out; overnight I became fanatical. I wouldn't even have a milkshake.