Porter Maberry, who competes as What's Gravity, is a 5'5" professional dunker and is widely reported to be the shortest man dunking professionally anywhere in the world. Sports Illustrated has described him that way, and the description has followed him through a decade of contests.
The height is the whole story, but not in the way people assume. A 5'5" dunker is not doing a scaled-down version of what taller dunkers do; he is doing something different. He has to generate enough height to get his hand meaningfully above ten feet with almost none of the reach advantage everyone else is working with, and then still have room to put a trick inside the jump. His phrase for it, given to FIBA before the Manila Masters, was heart over height.
He built his name on the FIBA 3x3 circuit between 2013 and 2015, competing across the World Tour and the All Stars events. He won his first major dunk contest in Lausanne, and he has said the atmosphere on that stage was what convinced him the discipline could carry a career.
His biggest result came on television. He won the first season of TNT's The Dunk King, and he closed it out by jumping clean over Shaquille O'Neal, who is 7'2". The visual of a man twenty-one inches shorter than the obstacle clearing him is the single image most people carry of Maberry, and it is a fair summary of the career. He returned for the second season and made the finale again, losing there to Guy Dupuy alongside Jordan Kilganon.
He came up through Team Flight Brothers, the touring group Chuck Millan started in 2004 specifically so that dunkers could get paid for performing, which for most of that generation was the only route to making dunking a job rather than a hobby.