The US singer, who turned 18 last month, is the youngest artist in history to write and record a theme for the franchise.
"It feels crazy to be a part of this in every way," said the star, who called the assignment "a huge honour".
"James Bond is the coolest film franchise ever to exist. I'm still in shock."
The last two Bond themes, Adele's Skyfall and Sam Smith's Writing's On The Wall (from Spectre), have both won an Oscar.