This is a list of sources of resistances.
Resistances
Slashing Resistance
Piercing Resistance
Bludgeoning Resistance
Fire Resistance
Elixir of Fire Resistance
Elixir of Dragonborn Prowess: Fire
Emblazoned Plate of the Marshal
Flame Enamelled Armour
Gloves of Fire Resistance when the wearer has 50% Hit Points or less (Inaccessible)
Grymskull Helm
Incandescent Staff
Infernal Robe
Helldusk Armour
Obsidian Laced Robe
Reverse Rain Cloak
Shield of Scorching Reprisal
Unwanted Masterwork Scalemail
Wavemother's Cloak once per turn until the wearer takes damage
Wavemother's Robe
Cold Resistance
-
Elixir of Cold Resistance- Elixir of Dragonborn Prowess: Frost
Icebite Robe
Robe of Summer-
- Wavemother's Robe
Lightning Resistance
-
Elixir of Lightning Resistance- Elixir of Dragonborn Prowess: Lightning
Gloves of the Automaton for 
Duration: 10 turns after using Circuitry Interface
The Sparkswall-
Thunder Resistance
Elixir of Thunder Resistance (Inaccessible)
-
Acid Resistance
Poison Resistance
Radiant Resistance
Necrotic Resistance
Force Resistance
Elixir of Force Resistance (Inaccessible)
Psychic Resistance
Elixir of Psychic Resistance
Psionic Ward Armour if the wearer is Gith
Silver Sword of the Astral Plane if the wearer is Gith
Multiple Resistances
Abyss Beckoners Demonspirit Aura: The wearer's summoned creatures have Resistance to all damage except 
Psychic.
Gain Resistance to all 
Bludgeoning, 
Piercing, and 
Slashing damage for Duration: 2 turns.
Circle of Bones Undead Ward: Allied undead within 6m / 20ft are Resistant to Bludgeoning, Slashing, and Piercing damage.
Creation's Echo Elemental Resonance: If the wielder deals 
Acid, 
Fire, 
Lightning, 
Radiant, or 
Necrotic damage, it becomes Resistant to that damage type for Duration: 2 turns.
When you or an ally gets hit with Acid, 
Cold, Fire, Lightning, or 
Thunder damage, you can use your reaction to give them Resistance to the attack.
Darkfire Shortbow Resistance to Fire and Cold damage.
Elixir of Universal Resistance Gain Resistance to all damage for Duration: 10 turns.
Put an ally in a protective coma. They become Resistant to all damage except Psychic.
Garb of the Land and Sky Mountainous Poise: While using 
, you also gain resistance to Bludgeoning, Piercing, and Slashing damage for Duration: 1 turn.
Resistance to Lightning and Thunder damage.- Hellrider's Pride Helm's Protection: When you heal another creature, it gains Resistance to Bludgeoning, Piercing, and Slashing damage dealt by weapon attacks for Duration: 2 turns.
Resistance to Physical damage.
Turn a creature's flesh hard as stone. It gains Resistance to all non-magical Bludgeoning, Piercing, and Slashing damage.
The Reviving Hands Aegis Palms: When you heal a creature, it gains Resistance to Bludgeoning, Piercing, and Slashing damage for Duration: 2 turns.
Ward an ally. They gain Resistance to all damage.
Resistance to all non-magical Bludgeoning, Piercing, and Slashing damage, and Resistance to all Lightning and Thunder damage.
Resistance to all non-magical Bludgeoning, Piercing, and Slashing damage.
Resistance to all non-magical Bludgeoning, Piercing, and Slashing damage.
Resistance to all non-magical Bludgeoning, Piercing, and Slashing damage, and Resistance to all Acid damage.
Transform yourself and all nearby party members into tiny clouds of mist to avoid attacks. You become Resistant to all non-magical damage.
Vulnerability
Arsonist's Oil Targets with Resistance to Fire damage become vulnerable to it instead. Targets with Immunity are unaffected.
Bhaalist Armour Aura of Murder: Enemies within 
2 m / 7 ft become Vulnerable to Piercing damage, unless they are Resistant or Immune to it.
Bloodthirst Exploit Weakness: (Main Hand Only) Creatures hit with this weapon receive Vulnerability to Piercing damage.- Vulnerability to Bludgeoning, Thunder, and
Force damage. 
Vulnerability to all damage.
Vulnerability to Cold and Lightning
Allies Only
Amulet of the Unworthy Vulnerability to Bludgeoning- Reverse Rain Cloak Vulnerability to Cold and Lightning
- Wavemother's Cloak Vulnerability to Cold and Lightning once per turn until the wearer takes damage
Immunity
Miscellaneous
Abdel's Trusted Shield Allows wielder to cast 
once per short rest, which grants Resistance to Physical damage from ranged weapons for 10 turns.
Bonespike Gloves Exoskeletal Reinforcement: Your attacks ignore Resistance to Slashing, Piercing, and Bludgeoning damage.
Cindersnap Gloves Allows wielder to cast once per short rest, which grants Resistance to Physical damage from ranged weapons for 10 turns.
: Spells you cast ignore resistance to a damage type of your choice.
When you fall, you can use your reaction to gain Resistance to Falling damage.
