Aged only 16, Maci Currin, from Austin, Texas, has legs measuring an incredible 53 inches - smashing the previous record of 52.2 inches held by Ekaterina Lisina, of Russia.
The 6ft 9in aspiring model also has an inseam of 43 inches and has to stoop to avoid banging her head when walking through doors.
Maci was only 19 inches when born, but a series of growth spurts meant she rocketed to 5ft 7in by the time she was nine years old.
Maci's mother Trish, 55, told Barcroft TV: "I realized that she was taller than the average kid at about 18 months, when she was already 2ft 11in.
"She was at a Mother's Day Out and I went to pick her up and she was already a head above the other children.
"There's a picture of her standing next to another little girl and she looked like she was two years older.
"There were four or five years that she grew like five inches in a year, which is a lot. She has always had long legs. I used to think I had long legs but not anymore."