In which weight class did Manny Pacquiao win his first world title?

Manny Pacquiao won his first world title in the flyweight division.

Pacquiao captured the WBC and lineal flyweight championships on December 4, 1998, when he knocked out Thailand's Chatchai Sasakul in the eighth round. Pacquiao was 19 years old and still early in his professional career. The victory gave him his first major world championship and established him as a serious international contender.

The flyweight division historically covers fighters weighing no more than 112 pounds, or 50.8 kilograms, under the traditional professional limit. Pacquiao later moved through multiple divisions, eventually winning major world titles from flyweight to light middleweight. That upward journey is why his first title is sometimes confused with his later championships in featherweight, lightweight, or welterweight.

Pacquiao's achievement became historically unusual because he won major world titles in eight weight divisions, more than any other boxer. His first championship, however, came at the smallest division associated with his world-title career: flyweight.