A common feature of pro wrestling scripted matches is the referee getting knocked out ‘by mistake’ or on purpose.
But, in boxing has a fighter ever punched the referee? Either by accident when the ref is trying to break up two fighters or else the boxer loses it during the heat of the fight and throws a deliberate punch to hit the referee.
It has happened. I recall seeing cases where a ref was hit, don’t recall one where the ref was knocked out but it could have happened. Usually when a ref is hit the boxer is already pulling his punch or a wild swinging connect unlikely to knock someone down or out, but not at all impossible. Occasionally boxers get knocked down or out by that kind of ‘lucky’ punch.
Peter Müller, called “de Aap”, “the monkey” in Cologne dialect, a quite famous German pro boxer, famously knocked out the ref in a fight in 1952 and then went totally wild and attacked everyone. It’s a legendary story here. It’s a pity that this footage doesn’t show the crucial moment, but it captures his rage, and I can contest to have seen the actual punch.
ETA: I have seen Peter Müller knocking out the ref with a clear punch numerous times on TV, because it’s a legendary story, but it seems like any online footage omits the punch, probably because of legal reasons. This is the best I could find.
I used to watch a lot of boxing, especially with my Dad, who loved boxing. We saw a number of referees get hit, including the Willie de Wit fight noted above by @Horatius . De Wit is a judge now - not a boxing judge, like a judge in the courts.
I saw a ref get knocked down at a live event once; he wasn’t really hurt, fortunately.