When the UFC made its debut 30 years ago, it was very different to the slick, refined operation we have today.
There were minimal rules, and perhaps most notably, no weight classes. It wasn't until UFC 12 in 1997 that weight classes were introduced, and it wasn't until as recently as 2006 that the lighter weight classes were introduced following the UFC's acquisition of World Extreme Cagefighting, which boasted champions including Jose Aldo, Urijah Faber, and Dominick Cruz.
The UFC now has eight weight divisions for men and four for women.
Here are all of the weight classes and their current champions.
Since Francis Ngannou left the UFC, vacating his title, the heavyweight division is awaiting a new champion.
Former light-heavyweight champion Jon Jones will finally make the step up to take on former challenger Ciryl Gane at UFC 285 on 4th March.
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Jiri Prochazka's injury threw the division into turmoil, vacating his title, with would-be challenger Glover Teixeira also pulling out of the fight. Magomed Ankalaev and Jan Blachowicz fought out a draw, leaving the title without a holder, before Jamahal Hill beat Teixeira at UFC 283.
Announced 28th January, Alex Pereira's first defence of the UFC middleweight title will be, as expected, Israel Adesanya. Former champ Adesanya held the title for three years, cementing himself as one of MMA's all-time greats, before suffering a humbling knockout to Pereira, who'd twice beaten him in kickboxing bouts.
The pair will clash for the fourth time, and second time in the Octagon, on 8th April at UFC 287
For so long one of the hard luck tales of the UFC, Leon Edwards finally got his title shot against P4P number one Kamaru Usman, winning with a devastating knockout with a minute left of the fight.
Usman had looked nigh-on unbeatable during his title reign, and the pair are set to meet again in London at UFC 286 on 18th March.
Islam Makhachev had spent a long time on the outside looking in as the UFC's most competitive division battled it out for the title, with Charles Oliveira eventually establishing himself as the top dog. But Makhachev was always waiting in the wings, looking like a champion in waiting.
The pair met, with Makhachev capturing the title, and he made his first defence against Alexander Volkanovski at UFC 284 on 12th February, narrowly out-pointing the Australian.
Alexander Volkanovski claimed the featherweight title in 2019 and has clung on like a rabid dog ever since. He out-pointed Max Holloway to claim the belt, doing so two more times (Holloway, remember, has only been stopped once in 30 MMA fights), also beating Brian Ortega and the Korean Zombie.
The featherweight division isn't stacked with potential contenders, and the Aussie has beaten the top contender three times, so Volkanovski stepped up to lightweight in an attempt to become a two-weight world champion against Islam Makhachev, losing via decision, and will likely have to defend his title against Yair Rodriguez later in the year.
Yair Rodriguez has hung around the featherweight division for a number of years, with his only UFC losses coming to Frankie Edgar and Max Holloway.
With Volkanovski stepping up to lightweight, an interim title fight was made between Rodriguez and Josh Emmett, with Rodriguez winning by submission in the second round, now eyeing a unification fight with Volkanovski later in the year.
It's not often someone who's won three consecutive title fights is disputed as the best fighter in the division, but Aljamain Sterling finds himself in that position.
Having won the title via DQ against Petr Yan, Sterling controversially defended it against Yan via split decision, before beating a clearly injured TJ Dillashaw.
After years of Demetrius Johnson dominance, Henry Cejudo became the king of the 125lbs division before hanging up the gloves, leaving a void at flyweight. Brandon Moreno and Deiveson Figueredo fought out a quadrilogy, with Moreno finally coming out on top to settle the score once and for all.
While Amanda Nunes was defeated at the more competitive bantamweight, it's hard to see where a loss at featherweight will come. Since destructively defeating Cris Cyborg in 2018, Nunes has only defended twice - against Felicia Spencer and Megan Anderson in 2020 and 2021.
Not since the days of Ronda Rousey has the women's division seen a champion as dominant as Amanda Nunes.
But since Rousey lost the title to Holly Holm, Holm lost to Miesha Tate, who then lost to Nunes. The first successful defence of the women's bantamweight title since Rousey was by Nunes against, of all people, Rousey herself, and it's a title she never looked like losing.
That was until her shock defeat to Julianna Pena, before avenging the loss and reclaiming her crown seven months later in July 2022.
While Amanda Nunes dominates the heavier women's weight classes, the 125lbs division belongs to Valentina Shevchenko, and has since 2018.
As invincible as Nunes looks at 135, Shevchenko looks her equal at 125, making seven straight title defences.
In fact, in her last 18 fights, Bullet has only lost to Nunes, and will be looking to extend her streak against Alexa Grasso at UFC 285.
After losing her crown to Rose Namajunas, and controversially losing the rematch, Zhang won her next two fights to regain the title against Carla Esparza.
Her next date in the Octagon isn't set, but fans will be keen to see the trilogy fight between Zhang and Namajunas in 2023.