[RPG] Can you help a prone character to stand up

dnd-5eprone

I had a player who wanted to help someone else stand up before his turn starts so he can reach the enemy. Is this written in the D&D 5e rules? If not, how would you rule this?
I am thinking of using the helping character's movement instead.

Best Answer

Yes you can

PHB Chapter 9: Combat, page 193, emphasis mine:

Your character can do things not covered by the actions in this chapter, such as breaking down doors, intimidating enemies, sensing weaknesses in magical defenses, or calling for a parley with a foe. The only limits to the actions you can attempt are your imagination and your character's ability scores. See the descriptions of the ability scores in chapter 7 for inspiration as you improvise.
When you describe an action not detailed elsewhere in the rules, the DM tells you whether that action is possible and what kind of roll you need to make, if any, to determine success or failure.

D&D is not like a computer game. Your player can announce various things, including "I'm trying to help him stand up". It is your job as a DM to make a ruling instead of just saying "no you can't do this because, you know, this action isn't in the list".

RAW, the PC spends their Action trying to do this. You might ask the player to make an ability check, if there is a chance of failure:

Actions in Combat

When you take your action on your turn, you can take one of the actions presented here, an action you gained from your class or a special feature, or an action that you improvise.
When you describe an action not detailed elsewhere in the roles, the DM tells you whether that action is possible and what kind of roll you need to make, if any, to determine success or failure.

I'd say it should be an automatic success in this case — the action itself is trivial, and spending an Action in combat is already a decent price. Just keep your players informed: "Yes you can help him, but you won't have time to do anything else in this turn. Will you do this?"

It should not go for the price of just the helper's movement thought — firstly, because it contradicts the rules (you must spend an Action and you can't really "transfer" your movement feet to another character), and secondly, it creates a precedent of doing something useful in combat almost "for free" (you have plenty unused movement in combat usually).