From Space.com:
It’s 2017, and a thunderstorm shoots off a lightning bolt. What’s so special about that, you ask? Well, the bolt is an astonishing 515 miles (829 kilometers) long.
Using archival satellite data, researchers just officially confirmed the length of this enormous bolt of lightning that stretched from Texas to Missouri. It sets a new world record, besting the previous title holder — a 477-mile (768-km) bolt from 2020 — by 38 miles (61 km).