Jason J. Popson (born November 2, 1971 in Cleveland, Ohio) is an American vocalist for the band Mushroomhead taking the stage name J-Mann. He is identified by his white face paint with black accents resembling a zombie-like mime or the face paint worn in the movie Dead Presidents.
Popson quit Mushroomhead in mid-2004 due to being overworked and his father being ill. Though it was previously confirmed that Popson would be featured on Mushroomhead's new studio album Beautiful Stories For Ugly Children, it was revealed in an interview with Mushroomhead's lead singer Jeffrey Nothing that he would no longer be on the album. No specific reason was given. Popson began making periodic stage appearances during Mushroomhead songs some time around 2008 and has since performed with them numerous times, including filling in for an entire show in 2011 when Waylon Reavis was sick and unable to perform. As of 2013 J-mann announced on his personal Facebook that he has returned to the band.

Popson is an actor and musician who has been involved with the industry since the early 1990s. It has been hinted lyrically and in vague interviews that he was raised by a single parent — his mother — following the departure of his father from his life at a young age. However, Popson later regained a relationship with his father, which played a pivotal role in him leaving Mushroomhead.

Popson's father, John, died in September 2006 and in memory of his father, Popson performed a concert at Peabody's Down Under in Cleveland, Ohio on September 29, 2006. The concert acted as a benefit for his father's funeral, and featured Popson performing songs from many of his previous and current bands.

Popson is now in a groove metal band with former Strapping Young Lad/Death drummer Gene Hoglan called Pitch Black Forecast which also features Robert Reinard on guitar and Craig Martini recording studio bass. Martini performed in Pitch Black Forecast's inaugural shows, but was then replaced by Steve Rauckhorst for live shows. The band also added guitarist Tom Shafner to its lineup. Pitch Black Forecast was formerly known as Absentee and the group's first release was on Popson's Melvins tribute album — released through his record label Fractured Transmitter — titled We Reach: The Melvins when the band performed a cover of the song "Revolve." Pitch Black Forecast officially released its new EP "Burning in Water ... Drowning in Flame" on Aug. 11, 2012. It was released independently.

Popson's newest project, titled Scelestus (pronounced sha-less-tus), released an EP through Megaforce Records on May 10. The metal project also features Steve "Skinny" Felton of Mushroomhead and Tommy Church from Mushroomhead and Tenafly Viper. An LP is said to be in the works, but no official release date or confirmation has been reported. In 2013, he confirmed his return to Mushroomhead.