Although gliders go back to the year 800, I assume you are asking about the engine-based glider and that one is credited to the Wilbur and OrvilleWright also known as the Wright Brothers. They devised several different models beginning with the kite model, and from then on built the first engine-based glider in December, 1903, in the morning, near Kitty Hawk, NC. Which is why North Carolina's license plates read "First in Flight"
HOWEVER you might have heard that there is a debate on whether North Carolina should earn that title, because the first STEADY pilot-managed flight by the Wright Brothers was made in 1905 in Ohio, their native state. So whether NC should be the "first" theoretically, or Ohio, that is something for the historians to try and solve, though I am sure someone on Enotes can tell us more about that.