Glossary: One-Punch Knockout

A one-punch knockout is the when a fighter throws one punch during a fight and that punch results in a knockout.

Note that that it will be the first punch a fighter throws.*

The stats would looks something like:

Fighter A:
Punches thrown: 1
Punches landed: 1
Connect rate: 100%

It's irrelevant what the other fighter does. But, generally, the one-punch knockouts are the first (and only) punch thrown by either competitor in a match.

The term "one-punch knockout" is often used incorrectly by casual fans and UFC commentator Mike Goldberg to refer to a lone punch (not part of a combination) that results in a knockout. By definition a knockout punch is a single punch thrown that knocks someone out, so technically they are right, however if you're going to do that, you may as well note that even in a combination, a single strike will be the one that causes the knockout.**

* It's possible in MMA that a fighter follows their opponent to the ground and continues to pound on them - this will still be a one-punch knockout.

** I suppose it's possible to punch someone with both fists simultaneously. I've never seen it actually used in a competition before though.