Life steal (LS) is a stat that restores health to the attacker on all basic attacks, including effects or abilities that modify the basic attack (such as NasusSquare Nasus' Siphoning Strike Siphoning Strike or Spellblade). The percentage value is the amount of HP restored from the attack after modifiers and mitigation (i.e. it is calculated from the effective damage done by the basic attack).
On-hit effects do not apply life steal in addition to the basic attack. However, abilities such as FioraSquare Fiora's Lunge Lunge and EzrealSquare Ezreal's Mystic Shot Mystic Shot that apply on-hit effects also apply life steal (these effects are treated as basic attacks and abilities at the same time).
Life steal is calculated from the actual damage done to an enemy, after armor and all other forms of damage reduction.
All champions have 0% base life steal. It can be increased with items, runes, and by some champion abilities.
The phrase "life steal" for the effect is not accurate, because no (additional) HP is "stolen"; rather, the effective damage that was already dealt (with or without life steal) becomes a source of healing to the attacker. In other words, life steal does not change or increase damage, but it does add a healing effect.

Increasing life steal

The following is true life steal. It does not benefit from Heal power Heal Power.

Items

Item Cost Amount Availability
Bilgewater Cutlass item Bilgewater Cutlass1500 Gold10 %Common
Blade of the Ruined King item Blade of the Ruined King3200 Gold12 %Common
Doran's Blade item Doran's Blade450 Gold3 %Classic
Guardian's Hammer item Guardian's Hammer950 Gold10 %Howling Abyss
Mercurial Scimitar item Mercurial Scimitar3600 Gold10 %Common
Ravenous Hydra item Ravenous Hydra3500 Gold12 %Common
Vampiric Scepter item Vampiric Scepter900 Gold10 %Common

Champion abilities

Runes

Increasing attack drain

The following is really similar to life steal, but is not really life steal. It benefits from Heal power Heal Power.

Items

Champion abilities

Runes

Notes

See Healing reduction for more information.

Trivia

Last updated: November 21, 2017 - V7.23

References