Who is Carlos Ulberg? Six months ago the answer would have started with kickboxing footnotes and Contender Series highlights. Today it starts with a title belt. The 35-year-old New Zealander, born in Auckland to a family of Samoan, Maori and German descent, knocked out Jiri Prochazka in the first round of UFC 327 on April 11, 2026, at the Kaseya Center in Miami to become the promotion’s light heavyweight champion.
Ulberg fights under the nickname Black Jag, and the answer to what is Carlos Ulberg’s nickname is exactly that, no elaborate backstory attached, just a name that stuck from his early kickboxing days. He trains out of City Kickboxing in Auckland, the same gym that produced former champions Israel Adesanya and Alexander Volkanovski, and his 6-foot-4 frame with a kickboxer’s footwork has made him one of the more distinct strikers in the 205-pound division.
The path here was not a straight line. Ulberg lost his UFC debut to Kennedy Nzechukwu by knockout at UFC 259 in March 2021. Everything since has gone his way. Counting from that loss on March 6, 2021, through the Prochazka finish on April 11, 2026, Ulberg went 1,862 days without a defeat, a stretch covering ten consecutive wins over Fabio Cherant, Tafon Nchukwi, Nicolae Negumereanu, Ihor Potieria, Da Un Jung, Alonzo Menifield, Volkan Oezdemir, Jan Blachowicz, Dominick Reyes and finally Prochazka. That is close to five years and one month between losses, an unusually long uninterrupted run for a fighter competing in a division as top-heavy as light heavyweight.
The finish itself fit the pattern of his recent knockouts. Ulberg dropped Prochazka with a left hook and finished with follow-up punches at 3:45 of round one, a result official UFC event records confirm alongside a Performance of the Night bonus. It was a jarring result given Prochazka’s reputation for chaotic, hard-to-prepare-for output, and Ulberg addressed his own preparation directly in a UFC.com fight week feature. Asked about his approach to camp, he kept it simple. “Sacred. That’s what it is,” he told UFC.com. “That’s how I like to do it, is spend a bit of time on my own as well.”
Stylistically, Ulberg is closer to a pure kickboxer than most of his 205-pound peers. He prefers distance, timing and clean entries over wrestling exchanges or scrambles, and his power has carried him to first-round finishes in six of his last ten fights. Where Prochazka built a career on unorthodox angles and improvisation, Ulberg wins by making the technical version of the sport look simple. It is a style built over years of professional kickboxing before he ever set foot in the Octagon.
As of this writing, Ulberg is 103 days into his reign with no first title defense confirmed. The division around him is unsettled. Former champion Magomed Ankalaev looks to rebuild momentum this month in Abu Dhabi, a comeback fight covered in detail here that will help shape who eventually gets the next crack at Ulberg’s belt. Where Ulberg himself sits in the broader rankings picture, and how the promotion’s newer ranking system weighs a title win like his, is explained in this breakdown of the UFC rankings algorithm.
For now, the man who spent years as an afterthought in a crowded 205-pound weight class is the one everyone else is chasing. Ulberg has not said publicly who he wants next, and the UFC has not booked a defense. What he has done is remove any doubt about the first question people had when his name started trending. Who is Carlos Ulberg fighting next matters less right now than the fact that whoever it is will be facing a champion who has not lost in half a decade.
