Does casting Lightning Bolt in melee provoke an Opportunity Attack? [duplicate]

Question

Our Sorcerer wanted to cast a Lightning Bolt as their attack on a monster that had made it into melee with that Sorcerer. DM said could make the attack, but it would provoke an OA (that would likely kill the sorcerer).

Player argued that as a magic-using character they would be as adept as a Fighter doing a melee attack. The range being Self was integral to the issue. What lies beyond the initial target was not in question. AoE was not relevant.

DM ruled (and yes, whatever he decides is what we go with, I'm here looking for discussion of rules and logic of the situation), that it took enough time summoning the magic that the monster would get a free shot. Player countered that a successful attack would stop the spell anyway.

Player maintained that it was essentially a melee attack he was making as the range was less than 5 feet (starting with the caster) and should not provoke OA.

Which position is correct though? Does casting Lightning Bolt within an enemy's reach provoke an Opportunity Attack?

@Rubiksmoose This question is different enough from your provided generic answered question. Those who are versed in earlier version rules will benefit from the specifics of this question. As well as the specific differentiation between ranged attacks and the lightning bolt characteristics.

Answer 1

Casting spells never provokes an opportunity attack in D&D 5e. See the rules for Opportunity Attacks on the SRD:

Opportunity Attacks

In a fight, everyone is constantly watching for a chance to strike an enemy who is fleeing or passing by. Such a strike is called an opportunity attack.

You can make an opportunity attack when a hostile creature that you can see moves out of your reach. To make the opportunity attack, you use your reaction to make one melee attack against the provoking creature. The attack occurs right before the creature leaves your reach.

You can avoid provoking an opportunity attack by taking the Disengage action. You also don’t provoke an opportunity attack when you teleport or when someone or something moves you without using your movement, action, or reaction. For example, you don’t provoke an opportunity attack if an explosion hurls you out of a foe’s reach or if gravity causes you to fall past an enemy.

That bolded part is the only thing that grants an opportunity attack, and it requires you to move out of reach of an opponent. This makes them work very differently from previous versions. You can freely engage with an enemy through large threat ranges, and move around inside someone's threatened space, as long as you don't leave it.

Spell never provoke, and neither do ranged attacks. You do have Disadvantage on any attack rolls made with ranged attacks and ranged spells while in melee, but that only matters for spells that make any. Lightning Bolt isn't one of them.

Answer 2

Erik's answer covers most everything that's applicable to your questions, but a few things I would like to add for your future discussion with your DM:

• A monster with the Mage Slayer feat would be able to make a melee weapon attack against the Sorcerer with it's reaction. Per the definition of a reactions and when they occur, this attack would occur immediately after the spell being cast. Being able to do this a specific feature of the Mage Slayer feat, and granting it to everyone could reasonably increase a monster's CR against caster heavy groups.
• The DM's issue with the range of Self should not be construed to mean anything other than that the spell has to originate from yourself, as opposed to Fireball, which is a 20' radius sphere within 150' of the caster. Bear in mind, many buff spells, including smite enhancers for Paladins use a range of Self, so it very likely it is not intended for these spells with this range to provoke opportunity attacks lest it render an entire sub-category of spells pointless (or at least too risky to use).
• Your DM is likely recalling rules from previous editions, which are not applicable in 5e and their exclusion was likely deliberate by the designers. It's worth noting that casters' power has been scaled back substantially since 3.5, so your DM should be aware that adding an additional nerf of removing their ability to competently cast in melee range could be significantly unbalancing.