This list has been compiled by YouTube Music based on factors including YouTube views, engagement from music fans from across the world and YouTube Music analytics.
Topping the list is R&B songstress Mahalia, with slowthai joining other acts including Octavian, Grace Carter, Kojey Radical, Sam Fender, L Devine, Dermot Kennedy, Samm Henshaw and Jade Bird.
The list is dominated by individual singer songwriters who are pushing boundaries and, in some instances, creating new genres.
The list is also notable for not featuring any groups, comprising ten solo artists.
Speaking about his inclusion, slowthai said: “It’s a blessing to be shortlisted by YouTube Music for Ones to Watch in 2019.
“Love to YouTube and everyone else supporting me.”
Over the past year, slowthai has released a steady string of music, from the politically-charged North Nights / The Bottom, to unpicking vulnerable and toxic masculinity on Ladies and the stereotype-dismantling volley of Drug Dealer and Rainbow.
His music is unmistakably British, treading a line between grime, rap, dubstep and garage.
All follow in the footsteps of acts including Ed Sheeran and Du Lipa who found fame on the world’s biggest music platform.
Azi Eftekhari, head of music partnerships at YouTube UK, said: “This is a year of UK artists doing their own thing.
“With the freedom musicians now have to express themselves not just sonically, but visually, it’s perhaps unsurprising that this list only features solo artists, many of whom are genuinely pushing artistic and visual boundaries.
“For example, Kojey, Octavian and slowthai are arguably redefining UK rap as a genre and acts like Mahalia, L Devine and Grace Carter - while they undeniably have huge commercial appeal - don’t conform to the conventional expectations of a pop act.
“One thing is certain - YouTube continues to be an unmatched launch pad for emerging artists, and 2019 is set to be a huge year for home-grown UK talent.”
Music fans can listen to YouTube Music’s Ones to Watch 2019 artist spotlight via the YouTube Music App.
In October, slowthai announced the Brexit Bandit tour which will see him play across the UK and Europe in March and April next year.
The closest gig to his hometown is at Birmingham’s O2 Institute on Wednesday, March 27.
For more details, visit https://slowthai.com and https://www.youtube.com/user/slowthai