A heartwarming video has emerged of a woman asking her stepfather to legally adopt her on his birthday.

In the video, shot in Celina, OH, USA on May 13, the stepfather can be seen opening a package from which he pulls out a long heartfelt letter that she reads out to him.

At the end of the letter she asks him to open a second enveloppe in which adoption papers are enclosed.

"My stepfather has been an incredible inspiration to me and he has helped me through so many things," she wrote online.