With only one free hand, can I still cast spells with somatic components?

Question

I have a doubt about this. I have had various answers and they contradict each other so I would like some clarity on this.

I am a Cleric, I have a shield (which is also my focus), I want to wear my shield in battle to benefit from the +2 AC and I want to be able to cast spells. I'm not holding anything in my free hand.

Is a Cleric who is a) proficient in Shields and b) trying to cast a spell with a somatic component able to do so, if they only have one hand free?

That is, without having to doff the shield and suffering an AC penalty. I seem to remember there being a rule about needing to have at least one hand free to cast spells?

Thanks for your help with this.

Answer 1

Yes

Spellcasting only requires the use of one hand.

Somatic (S) Spellcasting gestures might include a forceful gesticulation or an intricate set of gestures. If a spell requires a somatic component, the caster must have free use of at least one hand to perform these gestures.

Source: 5e SRD

Note that you don’t necessarily need a free hand; The rules on material components imply you can use the hand holding your spellcasting focus (in your case, your shield) to perform somatic components:

A spellcaster must have a hand free to access a spell’s material components—or to hold a spellcasting focus—but it can be the same hand that he or she uses to perform somatic components.

Answering the last bit of the question:

I seem to remember there being a rule about needing to have at least one hand free to cast spells?

Yes, but only for spells requiring (S) components. There is no general rule that all spells require a free hand, and there are plenty of rules without somatic components such as Wish

Note that the 5e SRD is official material published by WoTC, but the website I’ve linked to itself is not run by WoTC; Rather it is a more convenient display for this official WoTC document published under the OGL.

Answer 2

Directly from the PHB pg 203 (emphasis mine) when discussing somatic(S) spell components:

Spellcasting gestures might include a forceful gesticulation or an intricate set of gestures. If a spell requires a somatic component, the caster must have free use of at least one hand to perform these gestures

Therefore if your character is holding a shield, in one hand and their other hand was empty, they would be able to cast spells that included somatic components.

For your case, where your shield is your spell casting focus, you do not even need a free hand. Also stated on the same PHB page mentioned above (emphasis mine) under the Material (M) component section it states:

A spellcaster must have a hand free to access a spell’s material components—or to hold a spellcasting focus—but it can be the same hand that he or she uses to perform somatic components.

Answer 3

The accepted answer provides the solution, but I'd like to add that an example about a cleric wearing a mace and a shield was used in Sage Advice to explain that it's possible to hold both items to cast a somatic and material spell:

A cleric’s holy symbol is emblazoned on her shield. She likes to wade into melee combat with a mace in one hand and a shield in the other. She uses the holy symbol as her spellcasting focus, so she needs to have the shield in hand when she casts a cleric spell that has a material component. If the spell, such as aid, also has a somatic component, she can perform that component with the shield hand and keep holding the mace in the other.

Additionally, and pertinent to the original question, the aforementioned response in Sage Advice offers an example of a spell with only the somatic component:

If the same cleric casts cure wounds, she needs to put the mace or the shield away, because that spell doesn’t have a material component but does have a somatic component. She’s going to need a free hand to make the spell’s gestures. If she had the War Caster feat, she could ignore this restriction.