Millie Bobby Brown Mourns 'Godzilla vs. Kong' Costar Kayle Hottle's Sudden Death

Millie Bobby Brown is among the sea of fans who are gutted by Kaylee Hottle's sudden death ... and she's paying tribute to her late costar, who died in a car crash.

Millie starred alongside Kaylee in "Godzilla vs. Kong" ... and after Kaylee's death Tuesday, Millie took to Instagram to remember her fallen friend.

MBB shared an image of Kaylee from their movie and said Kaylee would be "deeply missed." She also said she was "devastated" to learn Kaylee died.

Rebecca Hall, who played Kaylee's mom in 'Godzilla,' also mourned Kaylee online.

Rebecca shared a few behind-the-scenes snaps from the film ... saying, "Devastated to hear this news. My heart goes out to your family. You will be missed, Kaylee."

Kaylee was a passenger in a car that crashed into a ditch Tuesday morning ... she was unconscious when first responders found her and was rushed to a hospital, where she died.