Ah. As said introvert in such a relationship, let me offer a few thoughts.

* I'm guessing that if you are taking him to parties of your choice, that means that it's all your friends and none of his friends. So he walks into a room full of people, none of whom he knows or seems to have anything in common with. Think about how you would feel if you were in a room full of people who speak a strange language that you are totally unfamiliar with. The next time you take him to such an event, before you go flitting around the room, spend some time together with him, introducing him to people you know, and help to make conversations that include him. Don't just go off socializing and abandon him the minute you walk in the door.

* Try to assemble some social activities that include some of his friends. Or maybe even take an interest in some of his activities. These days, even introverts generally know lots of people through social media, Internet gaming and the like. Does he go to cons or raves? You might consider them hopelessly silly, but try going to one. You'll meet a lot of types of people that you've probably never encountered before.

* When you go to parties, is he always the designated driver? Generally, alcohol loosens social inhibitions. You be the DD for once, and let him drink, and see what happens.

I look at the flow of "energy". For the extrovert, they take in energy from big parties and lots people and activity, afterwards they feel relaxed and recharged. For the introvert, such gatherings take away energy, afterwards they feel drained and stressed. A day alone on a hike or a secluded beach or just reading a book, just the opposite.

I've heard of one exercise, where people were grouped as introverts and extroverts, then made a list of questions to ask the other group. The introverts' questions are almost all a variation of "How do you stand all the noise?" And the extroverts' reply is, of course, "What noise?"

I'm the introvert, husband is the extrovert. I'm the kind of introvert that likes being around people, but it has to be structured around an activity I'm excited about, like dancing or hiking. Unstructured "walk around with drinks and chat and meet new people" parties are my nightmare.

Eventually we just agreed to lead separate social lives. He does what he wants. I do what I want. And then we schedule one night a week to do things we BOTH like together and tell each other stories of all the separate adventures we had that week.

Of course, if there's a family function he really wants me at or a wedding, I'll go with him. But the run-of-the-mill birthday party or bar hangout, I'll just skip and he has a fine time without me. I'll go to a dance social or hiking meet-up instead and have a fine time without him.

So many people assume that "Couples" need to do everything together and "compromise" by doing things they hate for each other. Keep that compromising to a minimum and have your separate social lives. Anyone who tells you that's wrong is probably miserable in their own relationship and wants you to be miserable too.

For the extrovert, they take in energy from big parties and lots people and activity, afterwards they feel relaxed and recharged. For the introvert, such gatherings take away energy, afterwards they feel drained and stressed.

This is it, exactly. Lots of people don't get why, after a day of socializing with a large group, I don't want to leave my house the next day, even if I'm having a good time. "But we are having so much fun! Let's all grill out tomorrow!"

... but I need a day OFF.

"I'm the kind of introvert that likes being around people, but it has to be structured around an activity I'm excited about, like dancing or hiking. "

That's a point I forgot to bring up. Structured activities provide some relief for the introvert by imposing a set of rules for how people interact. There's less worry about looking foolish or having people regard you as boring. Sofar and I have discussed here before that we're both ballroom dancers. I can be an extrovert in the ballroom, because there's a set of social rules and expectations that govern interactions between people there. I agree with Sofar that I find unstructured gatherings, especially when it's mostly people that I don't know, stressful.

What do you call people that require balance? I need time by myself. I like time alone. I feel peaceful, happy, and energized,.. Ubtil I get too much alone time.

Every once in a while I also need that jolt of adrenaline that comes with a gathering. I can flit from stranger to stranger and get to know people. I can seek out that person that feels ill at ease and make them comfortable. I can have a blast.

And then I need that downtime again.

The worst for me is big sporting events or concerts. They have the noise. They have the crowds. What they don't have is meaningful personal interactions.

My husband lives for those things: the feeling of comradery with strangers just from cheering together without the need for personal interactions.

My sister calls herself and introverted extrovert. Perhaps I am the same. Perhaps I'm an extroverted introvert? Who knows?

'I attend networking events for work.'
So I take it many if not most of these people are strangers to both of them with the only thing in common is whatever industry she works in, so he really could be an outsider, introvert or no.
If it were her friends, he could become friends with one or two or their significant others, but this sounds to be more random or work related strangers each time. Torture.

I can be an extrovert in the ballroom, because there's a set of social rules and expectations that govern interactions between people there.

Yeah, it's so great. I'd NEVER drop into a random party or bar in a strange city, but I'll totally hit up a local dance social while I'm traveling. Because, while scenes vary, you basically know what you're getting into (but you still get the element of surprise by dancing with people you've never danced with). This is my introvert happy-place.

This is my introvert happy-place.

I'd like a sensory deprivation tank on the dark side of the moon

Sofar, that's me too. Within that environment, I enjoy learning the local variations and unfamiliar partners. In the cities where I travel to frequently, I've found places where I can go dance. Sure beats sitting in a hotel room watching TV.

"'d like a sensory deprivation tank on the dark side of the moon."

There is no dark side of the moon, really. Matter of fact, it's all dark.

I'm with you, luj.

Even as a young college student, I preferred to stay in my room reading or cross-stitching. I dragged myself to noisy, crowded events because in the USA everyone thinks you're "supposed to." I heard - all the time - how I needed to "put myself out there" and "get out of my shell."

Then I got older and decided I didn't have to do shit.

It's funny that in other cultures, like Japan, introverted behavior is more respected, and extroverts are seen as kind of like big bull-shitters who don't respect boundaries.