An unhinged woman with 13 priors was busted at Grand Central Station after allegedly waving a large knife at straphangers — months after getting arrested for threatening riders with a box cutter, cops said Thursday.

Transit officers were alerted to Caridad Wilkins, 48, threatening subway riders with a knife on the northbound 4 line just after 9 p.m. Wednesday, according to police and sources.

She was arrested at the next stop, Grand Central Station, and charged with reckless endangerment and menacing — and transferred to Bellevue Hospital for a psychiatric evaluation.

Wilkins, who has 13 prior arrests for various thefts, was picked up less than two weeks ago on the 6 train for petit larceny at the 125th Street station at East 125th Street and Lexington Avenue, police said.

Court records show she was cut free on supervised release.

Wilkins was also arrested in May after cops say she threatened a rider with a box cutter, also on the 4 line.

In that case, she was given supervised release but failed to appear for her follow-up hearing and a warrant was issued, court records show.

Wilkins was cut free again on supervised release after appearing in court for the warrant when she was picked up for the petit larceny in October, according to the court records.