I was wondering if an ancient dragon could grab someone in their claws, like not grappling, but literally holding them in their claws to restrain them.

They could, but it would require a grapple to grab that person. The grapple represents that person trying to escape being grabbed.

They can grapple definitely - but they can't restrain - because they don't have an Action that allows them to do that. If you want them to be able to do it - give them that action.

Would figure they could use their claws like chop sticks. And many people tend to have difficulty getting up if a dragon is resting a claw on their chest. Plus dragons are famous for flying away with the princess all the time. They just don't get fancy things that they get a powerful attack if they grapple. Or they can grapple each time they hit. They are quite old and have been more than likely impacted by the world too. Likely also attacked, so they know how to entertain themselves. (plus sometimes people don't have to kill everything they fight. And adventurers got fancy stuff)

That could work, but what I was imagining was the dragon grabbing them like a child would grab a superman action figure to make them fly.

Quote from Theomegaperson >>

I was wondering if an ancient dragon could grab someone in their claws, like not grappling, but literally holding them in their claws to restrain them.

 I’m struggling to understand the difference between what you are describing and a grapple.

With a grapple, you are attempting to hold someone in place and restrain their movement, but what i am imagining is that you are literally holding their entire body in your hand, similarly to a person holding a pencil with their closed fist, and the difference mechanically is that they cannot do any actions, other than maybe cast some spells that don't require you to have a hand free.  They could maybe also make a dc 30 or something strength check to escape.

Yea - you're talking about the difference between Grapple and Restrained. The only thing more potent than restrained is stunned or incapacitated or the like. And like I said - if you want to restrain you need to give the dragon the ability to do so because their monster stat blocks do not have it normally.

Within the rules, you are definitionally correct, but I don't see how someone who can't move their arms can whack you with a club.

Well - I mean - you did ask in the Rules and Game Mechanics forum...? If you want something more potent - you'll need the homebrew forum.

I guess you are correct.  I had just thought they must have put something in the rules that better quantified that.

Your best bet is to house rule that anyone grappled by an ancient dragon is either automatically restrained or incapacitated, due to the dragon's size and strength, using the rules for those conditions.

Quote from Theomegaperson >>

Within the rules, you are definitionally correct, but I don't see how someone who can't move their arms can whack you with a club.

 I think your base assumption that the dragon automatically would manage to hit all the dangerous bits with its grab is over the top tbh.

Quote from Theomegaperson >>

I guess you are correct.  I had just thought they must have put something in the rules that better quantified that.

 An ancient dragon is deadly enough as it is. If you give it an auto restrained feature then it starts to become a "thx, but no thx" regardless of potential reward.

Maybe the person getting grabbed makes a dex saving throw and if they succeed they can still attack the dragon with disadvantage, similar to grappling, and if the dragon tries to grab you you get a dex save, maybe dc 15 or something.

You mean similar to restrained. Grappled just sets your speed to 0.

Well, if you fail the dex saving throw that lets you get grabbed, but succeed the second one, it is the same as restrained, but if they fail the second one as well, then they can't take actions, unless it would make sense for you to do the action while not being able to move.

They can't wriggle?

Further up I said that on their turn they could make a check to see if they can escape, but given that they are trying to escape an ancient dragon's grip, it would be pretty tough.