Is Batman a ninja?

Sure. There's even that cartoon (anime style) movie about Ninja Batman, lol.

Batman wears a dark costume, is stealthy, is acrobatic, fights with a variety of martial arts (ninjutsu included) and uses batarangs just like ninjas use shruikans; does all that qualify him as ninja?

Yeah it was also mentioned I think

he's practically one.

Obviously

Are Deathstroke and Karati Kid Ninjas?

No, he's a gangsta, get ya facts straight.

He's partially a ninja.

Most of the time he's portrayed as one. Zack Snyder's Batman is not... actually that's the only contradictory one that immediately comes to mind.

He's whatever he wants to be

Yes

Yeah, I always looked at him as a high tech ninja, right after the world's greatest detective.

He isn't. No fiction I have seen/read have managed to actually get a ninja right.

@nyhybrid89: Yeah, a ninja detective.

This.

Even if he did ninja art hand style?

@plotweapon16255: You do know that the ninja's you see in most fiction isn't ninjas right..?

So?

@plotweapon16255: So.. He isn't even close to a Ninja. Noone in the DC/Marvel/Fiction is aside from those that actually want ninjas to be portrayed as they actually were in real life.

Well the word ninja comes from Japanese spelling of Bat. In ancient Japan, the first ninja, millions of years ago, learned most of their secret techniques from bats, cats and panda, so yeah... I mean, Bat... Man.... Bat... Man. Pretty compelling and completely non fabricated reasoning as to why Batman is in fact a ninja.

Yes, he was trained by ninjas at some point in his life. Probably been through and passed more trials and tests than any other ninja.

@monsterstomp: Not real ninjas

@byondeon: Is a Spartan warrior the same as an Athenian warrior? No, but they're both warriors. Doesn't matter what degree of status of ninja we're talking about, Batman is still a certified ninja.

@monsterstomp: He isn't a ninja. He is as much a ninja as Superman is a supervillain

He is definitely more of a ninja than Naruto, that is for sure.