Pacquiao, a Philippine senator who has been dividing his time between politics and fighting, made the announcement in a 14-minute video posted on his official Facebook page.
“I just heard the final bell. Boxing is over,” said an emotional Pacquiao, the only man to hold world titles in eight different divisions.
“I never thought this day would come as a I hang up my boxing gloves,” said Pacquiao, as he thanked his fans all over the world.
Known for his fast footwork and blistering speed of punches, Pacquiao was widely regarded as one of the top offensive fighters in the sport’s history.
Veteran promoter Bob Arum in 2010 said he was unmatched, and rated him better than Muhammad Ali. “His left and right hand hit with equal power and that is what destroys his opponents,” Arum told Reuters.
In August, the 42-year-old lost a WBA welterweight world title match against Cuban Yordenis Ugas.
Growing up in the south of the Philippines, Pacquiao’s family was dirt-poor, prompting him to do odd jobs to survive. He stowed away on a boat to the capital Manila as a teenager, where he started competitive boxing.
Pacquiao was among the staunchest allies of Philippines President Rodrigo Duterte, backing the leader’s bloody war on drugs and his bid to reintroduce the death penalty.
But their political ties soured after Pacquiao criticised Duterte’s friendly relationship with China and corruption in the government. In July, he was ousted as president of the country’s ruling political party.
Pacquiao started his political career with failed congressional run in 2007. He won a seat at the lower house of congress in 2010, representing the southern Sarangani province.
The two-term congressman was elected for a six-year term in the upper chamber in 2016.
(Reporting by Neil Jerome Morales Editing by Ed Davies and Lincoln Feast)