There are 17 recognized weight divisions in professional boxing. From the lightest to the heaviest, they are:

Strawweight (up to 105 lbs)
Light Flyweight (up to 108 lbs)
Flyweight (up to 112 lbs)
Super Flyweight (up to 115 lbs)
Bantamweight (up to 118 lbs)
Super Bantamweight (up to 122 lbs)
Featherweight (up to 126 lbs)
Super Featherweight (up to 130 lbs)
Lightweight (up to 135 lbs)
Super Lightweight (up to 140 lbs)
Welterweight (up to 147 lbs)
Super Welterweight (up to 154 lbs)
Middleweight (up to 160 lbs)
Super Middleweight (up to 168 lbs)
Light Heavyweight (up to 175 lbs)
Cruiserweight (up to 200 lbs)
Heavyweight (over 200 lbs)

These weight classes ensure fair and competitive matchups between boxers of similar size and strength. Understanding the boxing weight divisions is key for any fan of the sweet science.