AFB and looking for a fighting style or feat

[Gryndle]

I could have sworn there was either a feat or fighting style that did this

"When an ally within 5 feet of you is hit with an attack, you may make an attack as a reaction, targeting the original attacker."

Paraphrasing the wording of course.

Am I misremembering it? If it does exist, what is it called?

[JackPhoenix]

Sentinel feat, 3rd point:
"When a creature within 5 feet of you makes an attack against a target other than you (and that target doesn't have this feat), you can use your reaction to make a melee weapon attack against the attacking creature."

[strangebloke]

It's a really good feat for a character who can add a lot of damage on reaction, like a rogue or a zealot.

[Gryndle]

Sentinel feat, 3rd point:
"When a creature within 5 feet of you makes an attack against a target other than you (and that target doesn't have this feat), you can use your reaction to make a melee weapon attack against the attacking creature."

Thank you. That was bugging the crap out of me.