YES HE IS and everyone that says he is not is lying!! (:

Yep Yep he sure is plus hes AWESOME!!

He's the best ninja of the DC Comic's Unviverse!

He's half bat, half Ninja : Duh!!!!!

Another answer

He has martial arts and stealth training, but he is not a "ninja" because a ninja is defined as: "A covert agent or mercenary of feudal Japan specializing in unorthodox arts of war." Batman did not receive his training in Japan, nor was he a mercenary of feudal Japan.

In the movie Batman Begins, it shows that he had joined a vigilante group called the League of Shadows and received his martial arts training with them.

Answer

Batman has ninja training which is why is the batman. Most of his tactics and skills are of ninja. Batman did receive his training in Japan and it doesn't mean u had to be "Mercenary of Feudal Japan" to be ninja. That's like saying I graduated from the police academy but I'm not going to be a cop. Ninja in feudal Japan were Farmers/Peasants who were rebellious against the crooked government known as the shogunate. Ninja were Samurai and Samurai were Ninja. Samurai by day, Ninja by Night but not all. Ninja were rebellious citizens of Japan. Batman did receive his training in Japan. Batman's trained under his Sensei "Kirigi." At the end of the day, it doesn't matter, Batman is the best Comic Book Character ever!