Professional boxing career

Early years at Light Flyweight division

In 1995, the death of a young aspiring boxer and close friend Eugene Barutag spurred the young Pacquiao to pursue a professional boxing career. Pacquiao started his professional boxing career when he was just 16 years of age, stood at 4'11'', and weighed 98 pounds (7 pounds under the minimumweight division). He admitted before American media that he put weights in his pockets to make the 105 pound weight limit. His early light flyweight division fights took place in small local venues and were shown on Vintage Sports' Blow by Blow, an evening boxing show. His professional debut was a four round bout against Edmund "Enting" Ignacio, on January 22, 1995, which Pacquiao won via decision, becoming an instant star of the program.

Pacquiao's weight increased from 106 to 113 pounds before losing in his 12th bout against Rustico Torrecampo via a third round knockout. Pacquiao failed to make the required weight, so he was forced to use heavier gloves than Torrecampo, thereby putting him at a disadvantage.

Flyweight division

Following the Torrecampo fight, Pacquiao continued undefeated for his next 15 fights. He went on another unbeaten run that saw him take on the vastly more experienced Chokchai Chockvivat in flyweight division. Pacquiao knocked out Chockvivat in the fifth round and took the Oriental and Pacific Boxing Federation (OPBF) Flyweight title. After one official defense and two non-title bouts, Pacquiao got his first opportunity to fight for a world title. Pacquiao captured the World Boxing Council (WBC) Flyweight World Title (his first major boxing world title as well as the flyweight lineal title) over Chatchai Sasakul by way of knockout in the eighth round. He defended the title successfully against Mexican Gabriel Mira via 4th round technical knockout. However, Pacquiao lost the title in his second defense against Medgoen Singsurat, also known as Medgoen 3K Battery, via a third round knockout. The bout was held in Nakhon Si Thammarat, Thailand. Singsurat got Pacquiao on the ropes and lan ded a flush straight right to the body coiling Pacquiao over and keeping him there. Technically, Pacquiao lost the belt at the scales, as he surpassed the weight limit of 112 pounds.

Super Bantamweight division

Pacquiao with his trainer Freddie Roach at Pacquiao's Christmas and birthday bash, Los Angeles, California.

Following his loss to Singsurat, Pacquiao gained weight anew and skipped the super flyweight and bantamweight divisions. This time, Pacquiao went to super bantamweight or junior featherweight division of 122 pounds, where he picked up the WBC Super Bantamweight International Title. He defended this title five times before his chance for a world title fight came. Pacquiao's big break came on June 23, 2001, against former IBF World Super Bantamweight champion Lehlohonolo Ledwaba. Pacquiao stepped into the fight as a late replacement on two weeks' notice but won the fight by technical knockout and won the International Boxing Federation (IBF) Junior Featherweight World Title belt, his second major boxing world title. The bout was held at the MGM Grand Las Vegas, in Las Vegas, Nevada. Pacquiao went on to defend this title four times under head trainer Freddie Roach, owner of the famous Wild Card Gym in West Hollywood.

Featherweight division

On November 15, 2003, Pacquiao faced Marco Antonio Barrera at the Alamodome, San Antonio, Texas, in a fight that many consider to have defined his career. Pacquiao, who was fighting at featherweight for the first time, brought his power with him and defeated Barrera via technical knockout in the eleventh round and won The Ring Featherweight World Title (as well as the lineal featherweight champion), making him the first Filipino and Asian to become a three-division world champion, a fighter who won world titles in three different weight divisions. He defended the title twice before relinquishing it in 2005.

On November 24, 2003, the then Philippine President Gloria Macapagal-Arroyo conferred on Pacquiao the Presidential Medal of Merit at the Ceremonial Hall of Malacañang Palace for his knockout victory over the best featherweight boxer of the world. The following day, the members of the House of Representatives of the Philippines presented the House Resolution No. 765, authored by the then House Speaker Jose De Venecia and Bukidnon Representative Juan Miguel Zubiri, which honored Pacquiao the Congressional Medal of Achievement for his exceptional achievements. Pacquiao is the first sportsman to receive such an honor from the House of Representatives.

Six months after the fight with Barrera, Pacquiao went on to challenge Juan Manuel Márquez, who at the time held both the World Boxing Association (WBA) and International Boxing Federation (IBF) Featherweight World Titles. The fight took place at the MGM Grand Las Vegas, on May 8, 2004, and after twelve rounds the bout was scored a draw, which proved to be a controversial decision that outraged both camps.

In the first round, Márquez was caught cold, as he was knocked down three times by Pacquiao. However, Márquez showed great heart to recover from the early knockdowns, and went on to win the majority of rounds thereafter. This was largely due to Márquez's counterpunch style, which he managed to effectively utilize against the aggressive style of Pacquiao. At the end of a very close fight, the final scores were 115–110 for Márquez, 115–110 for Pacquiao, and 113–113. One of the judges (who scored the bout 113–113) later admitted to making an error on the scorecards, because he had scored the first round as "10–7" in favor of Pacquiao instead of the standard "10–6" for a three-knockdown round. In fact, the fight should be scored as split decision in favor of Pacquiao. Consequently, both parties felt they had done enough to win the fight.