Blade Ward

Abjuration Cantrip (Bard, Sorcerer, Warlock, Wizard)

Casting Time: Reaction, which you take in response to a visible creature targeting you with a melee attack
Range: Self
Components: V, S
Duration: Instantaneous

You trace a sigil of warding, imposing Disadvantage on the creature's attack roll against you.

Source: Bastions and Cantrips