MMA weight classes have been refined over the years, since the sport's inxception back in 1993 when a skinny 170-pound Royce Gracie did battle against huge heavyweights.
The list of UFC divisions is below:
Heavyweight 206-265 pounds
The history of the UFC Heavyweight division is as old as the organization. The first title in the UFC was awarded to Mark Coleman when he became the inaugural Heavyweight champ at UFC 12. Since then there have been 13 different champions and two interim champions. Randy Couture has reigned for the longest time (1,113 days) and the current title holder is Junior dos Santos.
Light Heavyweight 186-205 pounds
The Light Heavyweight division has had three champions that have defended the title at least four times. Frank Shamrock, Tito Ortiz, and Chuck Liddell all reigned as a dominant champion but it was Ortiz that holds the record at 1,260 days. Randy Couture is a two-time champion, and the current champ is Jon Jones.
Middleweight 171-185 pounds
The Middleweight division has had only had five champions in the history of the organization; Dave Menne, Murilo Bustamante, Evan Tanner, Rich Franklin, and Anderson Silva. The main reason for that is Silva; he has been the champion since 2006 and has defended the title nine consecutive times. Silva continues to be a dominant champion and looks like he will be for a while to come.
Welterweight 156-170 pounds
The Welterweight division has had eight different champions since Pat Miletich became the first champ in 1998. He went on to defend the title four times, one less time than Matt Hughes during his first dominant reign. Hughes was a two-time champion, a feat only duplicated by reigning champ Georges St-Pierre. St-Pierre has defended the title six straight times.
Lightweight 146-155 pounds
Jens Pulver became the first UFC Lightweight champion at UFC 30, defeating Caol Uno, but was stripped following a contract dispute. The second champion was Sean Sherk who became champion at UFC 64, but he was stripped following a positive test for banned substances. Then B.J. Penn entered the UFC Lightweight picture and reigned for 812 days, defending the title three times before Frank Edgar came along. Benson Henderson is the newly-crowned king of the division.
Featherweight 136-145 pounds
The UFC Featherweight division has only been in existence since Jose Aldo brought the WEC title with him to the UFC in 2010. He’s since defended that title three times.
Bantamweight 126-135 pounds
Like the Featherweights, the Bantamweights have only been in the UFC for a short time. To date Dominick Cruz has defended his title twice.
Flyweight <125 pounds
Starting in 2012, some of the top fighters weighing 125 pounds or less finally got a place to fight on even ground.
The first Flyweight Tournament began in controversy with a jusge scoring mistake voiding Demetrious Johnson's win over Ian McCall. They were set rfor a rematch to decide a finalist for the title (Joe Benavidez won the other semifinal).