Selena Gomez's beauty routine is scary effective ... because not only does it help her look great, it also provides a new mask ... just in time for Halloween.

The singer and actress was spotted out in Beverly Hills on Wednesday ... walking to her car in a white sweater with a black face covering over a white sheet mask.

Selena was fresh out of a beauty session ... and it looks like she got a facial. Hooray for self-care.

It's a rare afternoon off for the oft-busy superstar ... who has a break in filming "Only Murders in the Building," which has been in production overseas.

As you may know, a new season of the hit Hulu show premieres in December ... and, while the series hasn't been confirmed for a 7th season yet, it's expected to be picked up soon enough.

She's got more on the way too ... including the Cate Blanchett movie "The Origin of the World" and a project in which Selena will portray singer Linda Ronstadt.

It'll soon be back to work for Selena ... but at least she's got everything she needs for a killer ghost costume this Halloween!