It seems Lindsay Lohan has been UNBANNED from the Chateau Marmont ... 'cause she returned to the legendary L.A. hotel last night ... months after she was kicked out for stiffing the place on a $46k bill.

As TMZ first reported, Lohan got the heave-ho earlier this year after she ran up a crazy $46,350.04 tab on a 47 day bender that included 49 packs of cigarettes and more than $3k in minibar items.

LiLo had told friends the producers of her upcoming Lifetime movie, "Liz and Dick," had agreed to pay her bill ... but our sources say that was never the case.

It's unclear if the bill was ever resolved ... but it seems it's all water under the bridge ... 'cause last night she was allowed back on the premises without a problem.