Joseph is an American world champion runner who competes mostly in trail, mountain and snowshoe races.  He won the World Mountain Running Championships in 2016 and 2019.  He is the first Black American to not only make the Team USA World Mountain Running Team, but also the first Black American to win the USA National Mountain Running Championships and the World Mountain Running Championships.

Joseph has been a 31-time Team USA national team member.  He is the only Black American to be part of the U.S. Mountain Running Team at any level.  He is an 18-Time USA National Champion and is a 5-time Xterra World Trail Running Champion.

He is the American record holder at the Mount Washington Road Race.  In August 2016, Gray won the Pikes Peak Ascent in a time of 2:05, the fastest climb since 1995.  The following month, he won the World Mountain Running Championships which were held in Sapareva Banya, Bulgaria.  In April 2017, Gray won the RRCA Colorado State Championship 5K Non-Road Race, held in conjunction with the Hams and Hamstrings 5K.

On July 20, 2018, Joseph Gray ran the fastest known time (FKT) up Mount Antero from the bottom of FS road 277 to the top of Mount Antero in 1:23:10. He used a running power meter during the attempt.

Gray has the FKT on the Manitou Incline in Colorado Springs with a time of 17:45 verified with GPS.