A homeless man has been charged in Monday’s attack on an 8-year-old autistic boy who was standing inside a Financial District subway station, authorities said.

Alex Bienaime, 40, was charged with assault and three counts of acting in a manner injurious to a child under 17, police said.

The boy was standing with his mother and two younger siblings inside a waiting No. 3 train at Fulton Street station when the stranger approached.

Without uttering a word, the assailant punched the child in the back of the head and fled, police said.

Police received a number of anonymous tips from straphangers who said Bienaime is known to frequent the area, officials said.

Beinaime was busted at the Chambers Street station Tuesday afternoon.

He has 10 prior arrests on turnstile jumping, robbery and assault charges.