Justin Smith (born in Paterson, New Jersey), better known as Just Blaze, is an American hip hop music producer. Just Blaze has produced tracks for The Beastie Boys, Jay-Z, Usher, Kanye West, Busta Rhymes, Jadakiss, Memphis Bleek, Beanie Sigel, The Game, DMX, T.I., Fat Joe, Rhymefest, Ghostface Killah, M.E.D., Fabolous and Joe Budden. He also recorded several tracks for the popular video games Tiger Woods PGA Tour 2004 and NBA STREET VOL. 2 and is a playable character in the game as well.

A large part of Just Blaze's technique consists of altering the speed of samples, as well as adding in his own drum beat. In this way, he draws some of his influence from Wu-Tang Clan producer RZA, who has utilized sped-up soul samples in several of the group's beats. Just Blaze has used this technique with songs like "December 4th" from Jay-Z's The Black Album (which uses a sped-up sample of "That's How Long" by The Chi-Lites) and "Touch the Sky" from Kanye West's Late Registration (which uses a slowed-down sample of Curtis Mayfield's "Move On Up.") However, he doesn't always do this; on "Public Service Announcement (Interlude)" from The Black Album and Foxy Brown's "Foxy Lady", for instance, the speed of the sample used is left unchanged.

Just Blaze has recently started a record label, Fort Knox Entertainment which is distributed through Atlantic Records. His first artist is Saigon. He is currently producing Saigon's debut album, The Greatest Story Never Told. It is expected to be released in 2007. This will be the first album that he has predominantly produced; he has generally contributed a few beats at most to various artists, rather than collaborating with them through the duration of an entire album.

His brother is Daren Smith, aka DJ Poun'. He is a resident DJ at the Atlantic City 40/40 club.