Ariana Grande's supporting her boyfriend, Ethan Slater, by hitting Broadway to watch his latest role in "Spamalot" -- and that means coming face-to-face with tons of her fans for the first time in a long time.
The crowd was waitin' for the singer outside the St. James Theater Tuesday night, where Ariana was checking out Ethan's performance in the Monty Python musical -- she left the show with a pal, her Playbill and a "Spamalot" paper crown.
Obviously, word got 'round that Ari was catching the show on Halloween, because loads of folks greeted her once the musical was over, and a lot wanted to snap pics with the singer ... but it sounded like she was a bit nervous for people's safety and instead took to the car.
Ethan plays The Historian & Prince Herbert in the Broadway revival -- it officially opens later this month, so Ari and co. were on hand for the musical's first preview. Always good to be in the with the cast.
Her friend really got into the Halloween spirit, BTW ... taking in the show while dressed as Sir Galahad!
Sources close to Ariana tell TMZ ... she's been having more fun, and going out more often lately -- we're told it's clear she feels safer and more able to be herself in this new relationship.
As we reported, we got Ethan leaving court last week after handling divorce and custody proceedings with his estranged wife, Lilly Jay -- we asked him how things were goin' with Ariana, but, for now, he's keeping pretty tight-lipped.