Did any Muggles actively fight against Voldemort?

Question

This question got me thinking

Did any Muggle (full blown "pure blood" Muggle with no magic; not Squib nor any wizard with majority Muggle relatives) actively fight against Voldemort?

Many of the witches and wizards that fought in the BoH (Battle of Hogwarts) were the husbands, wives, relatives or children of Muggles.

These Muggles were not completely oblivious of the wizard world unlike general Muggles. They would definitely be worried if their loved ones were targeted by or involved in any way with Voldemort, and possibly try anything in their power to help them.

Has there been any instance of a Muggle actively fighting against Voldemort? By this I don't mean giving passive help (for eg, Tonks' father, who was a Muggle, allowing Harry to stay in his house until he could be moved to the Burrow in DH), but actively fighting Voldemort, DE, going around raising awareness about Voldemort, etc? Has that ever happened in canon (books PS to DH) or the extended universe (Pottermore, interviews, twitter, movies, etc)? Since the answer will possibly be short, we can include both WW (Wizard War) I and II.

(If there are any instances of a Muggle actively fighting for Voldemort, that can be included too. I am just assuming nothing like that could ever happen, as Voldemort would probably never recruit a Muggle.)

Answer 1

No Muggles fighting the Dark Lord have ever been mentioned.

There’s no mention of any Muggles taking part in the fight either against or for the Dark Lord. While it is theoretically possible, no instances of it were shown to the reader. Frank Bryce confronted him before being killed, but he wasn’t actively fighting to stop the Dark Lord from gaining power.

“I am calling you a Muggle,’ said the voice coolly. ‘It means that you are not a wizard.’

‘I don’t know what you mean by wizard,’ said Frank, his voice growing steadier. ‘All I know is I’ve heard enough to interest the police tonight, I have. You’ve done murder and you’re planning more! And I’ll tell you this, too,’ he added, on a sudden inspiration, ‘my wife knows I’m up here, and if I don’t come back –”
_{^{- Harry Potter and the Goblet of Fire, Chapter 1 (The Riddle House)}}

Of course, he wasn’t actively participating in the fight against the Dark Lord. He didn’t know (though he realized at least after he was killed) that the Dark Lord was a wizard, and he had no idea exactly who the Dark Lord was in the larger picture. He is a Muggle shown facing the Dark Lord, though.

“Is that right?’ said Frank roughly. ‘Lord, is it? Well, I don’t think much of your manners, my Lord. Turn round and face me like a man, why don’t you?”
_{^{- Harry Potter and the Goblet of Fire, Chapter 1 (The Riddle House)}}

He knows he’s in danger, but he doesn’t know exactly who he’s dealing with.

The closest thing shown is Arabella Figg, a Squib, in the Order.

The closest thing shown to a Muggle actively working to stop the Dark Lord from gaining power is Arabella Figg, who’s a Squib, not actually a Muggle. She of course wouldn’t count as a Muggle fighting the Dark Lord because she’s not one. However, she still has no magic. Therefore, it’s also theoretically possible for a Muggle who’s aware of the wizarding world to help the same way she did (though no Muggles are actually shown doing anything similar).

“I’m a Squib, as Mundungus knows full well, so how on earth was I supposed to help you fight off Dementors? He left you completely without cover when I’d warned him –”
_{^{- Harry Potter and the Order of the Phoenix, Chapter 2 (A Peck of Owls)}}

She isn’t shown doing anything against the Dark Lord specifically, but she does help rescue Harry from the Dementors, and helps get him acquitted when he’s on trial. What she does (at least what we know of it) would probably be classified as passive help. But she’s still the only member of the Order, an organization whose goal is to fight the Dark Lord, who can’t use magic.

Answer 2

There is a name I want to mention. It is not the answer you are looking for and @bellatrix’s answer is much more complete but it just felt unjust not to mention her name.

Petunia Dursley

She lost a sister in the first Wizarding War and she accepted Harry as her family which protected him from Voldemort and Death Eaters until he was 17. This is truly a sacrifice for her because it led to harm of her own kid( Dementor Attack) and many weird events that made her husband angry as he is depicted as a person who literally hates weirdness since page 1. She could just reject him first day in her doorsteps.

You are looking for active fighters but not everyone is a fighter as we know. She took care of Harry, she fed him for 17 years and promised Dumbledore to keep him safe. This is her role in the battle as a fighter and she is aware of most of the things and knows the danger.

Answer 3

The number of Muggles who even know that there is a wizard going by the name of Voldemort must be a very small number.

The Muggle Prime Minister knows that wizards exist, and that one of them is trying to take over, but he hasn't been clued in on the details.

It is likely that some Muggle spouses of wizards have been told more, and I am sure they are doing all that they can do, but that isn't a whole lot.