Millie Bobby Brown Banking Over $6 Million to Play Enola Holmes

Millie Bobby Brown's bank account is about to get even bigger ... because the 15-year-old actress is raking in more than $6 MILLION for her next big-screen role.

If ya didn't hear, Millie landed the titular role of Enola Holmes in the upcoming movie franchise about Sherlock Holmes' much younger sister -- who becomes a private detective herself.

According to her minor's contract -- obtained by TMZ -- the teenager gets $6.1 mil to star in the film but could fetch up to an $800k bonus if it performs well at the box office.

Oh, she also gets a producer credit, which comes with an additional base pay of $500k -- and her contract allows for her to travel via private jet. A-list move for MBB!!!

It gets better too ... if there's a sequel, Millie will bank another $7.5 million, at the very minimum. Now that's how you take a ten and turn it up to Eleven.

As we've reported ... huge salaries are becoming par for the course for the "Stranger Things" kids, but Brown's taking a huge step ahead of the rest with this fat payday.

"Enola Holmes" is set to release some time in 2020, and will costar Henry Cavill as Sherlock and Helena Bonham Carter as Mrs. Holmes.