Deflection is a defensive stat that can be acquired as a percentage of your Evasion and can be found on the right side of the passive tree and as a stat on Dexterity-aligned gear.

Deflection is a defensive stat that can be acquired as a percentage of your Evasion and can be found on the right side of the passive tree and as a stat on Dexterity-aligned gear.

Deflection is a defensive mechanic that can reduce the Damage taken from any incoming Hit, including unavoidable Boss abilities. Deflection also reduces the Damage taken from any Damaging Ailments that were inflicted by an incoming Deflected Hit. Similar to Evasion, the exact chance to Deflect also depends on the attacker's Accuracy.
Chance to Deflect is a separate stat from Evasion and is rolled in addition to Evasion making it a particularly potent defensive layer.
Note: Unlike Evasion, there is NO maximum chance to Deflect, meaning you can cap the stat and reach 100% chance to Deflect
The formula below is used to calculate the chance to Deflect provided by Deflection, where DD is the total Evasion Rating of the defender and AA is the total Accuracy Rating of the attacker.
A successful Deflection will lessen the incoming Damage of a Hit and any Damaging Ailments resulting from that Hit by 40% by default. The amount of mitigation provided by Deflection can be improved by rare modifiers such as
Trained Deflection.
Chance to Deflect can be acquired through modifiers on Dexterity-aligned gear as a percentage of your Evasion, which means high investment in chance to Evade will be required to take advantage of this defensive stat.

A Gain Deflection from Evasion stat on Gear

A small Passive Skill Tree node granting Deflection
The amount of Deflection gained as a stat from another stat such as Evasion deviates from the normal mechanics of gaining one stat as another stat in Path of Exile 2. Usually the term 'Gain' refers to gaining the stated percentage of stat A as stat B, but only resulting from the base of stat A, not inclusive of any scaling modifiers. This is not the case with Deflection. Instead, Deflection Rating gained from a stat such as Evasion Rating occurs after any scaling to Evasion Rating.
For example if a character had a total of 3000 base Evasion Rating from their equipped Gear and they had 200% increased Evasion Rating on the Passive Skill Tree, they'd have a total of 9000 Evasion Rating. If this character took a small node on the Passive Skill Tree granting the modifier 'Gain 6% Deflection Rating equal to Evasion Rating', they'd gain a total of 540 Deflection Rating.
Note: for this reason, modifiers that grant 'increased Deflection Rating' are very powerful, as they essentially multiply on top of your Evasion scaling modifiers to provide a boost to Deflection Rating.
The Tactician's
Polish That Gear Ascendancy notable and the Unique Boots Shankgonne each provide a method to obtain Deflection Rating from Armour instead of Evasion Rating.