Chamberlain Stops O'Leary to Capture IBO Lightweight Title

Mark Chamberlain captured the IBO super lightweight world title with a dramatic tenth-round stoppage of previously unbeaten champion Pierce O’Leary in a brutal and bloody battle at Dublin’s 3Arena on Saturday, August 1, 2026. The victory, which came before a roaring crowd of approximately 7,000, instantly became a contender for Fight of the Year due to its relentless action and dramatic momentum shifts.

Chamberlain, a challenger from Portsmouth, England, seized control early, dropping the Dublin native with a left hand in the second round and again with an uppercut late in the third. O’Leary, bleeding from the nose, beat the count both times and mounted a spirited comeback fueled by his home support. His resilience paid off in the seventh round when a powerful body shot sent Chamberlain to the canvas, swinging the momentum and setting up a tense final act.

Both fighters, visibly marked, traded blows in the closing rounds before Chamberlain found a final surge. With just over a minute remaining in the tenth, he landed a decisive combination that sent O’Leary reeling onto the ropes. Referee Leszek Jankowiak stepped in to stop the contest, handing O’Leary his first professional...