Watch: Matthew Semelsberger brutally flatlines Martin Sano in 15 seconds at UFC 266

Matthew Semelsberger finished his UFC 266 opponent Martin Sano in just 15 seconds of the first round. The UFC welterweight connected a brutal right hand to Sano's chin, which sent him crashing to the canvas.

Watch the brutal knockout below:

As Sano charged forward to land a left hook, Semelsberger, with faster hands, caught him with a clean right cross. Giving Sano no opportunity to bounce back, the Maryland native threw a devastating hammer fist that confirmed his resounding victory.

Semelsberger's 15-second knockout win tied him with Song Kenan for sixth spot in the list of fastest knockout wins at welterweight. The Chinese fighter also knocked out his opponent Bobby Nash in 15 seconds at UFC Fight Night: Bisping vs. Gastelum in 2017.

The record for the fastest knockout in the welterweight division, and in the UFC, belongs to Jorge Masvidal, who finished Ben Askren in 2019 in just five seconds.

Following his latest victory, Semelsberger has now improved his professional MMA record to 9-3.

The 28-year-old lost his previous fight against knockout artist Khaos Williams in June this year. Now that he has produced a highlight-reel KO, Semelsberger will be looking to find his way into the divisional rankings of a stacked 170-pound weight class.

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Matthew Semelsberger becomes the second UFC fighter with two KOs inside 20 seconds

Matthew Semelsberger is now only the second fighter in UFC history with two knockout wins in 20 seconds, according to the UFC 266 broadcast team. He previously finished Jason Witt in 16 seconds in March this year.

Matthew Semelsberger shares the unique record with none other than Anthony 'Rumble' Johnson. The former UFC star knocked Chad Reiner out in 13 seconds in 2007. He replicated the same feat once again when he fought Glover Teixeira six years later.