The 22-year-old skilful midfielder has made just three Premiership starts for Steve McClaren's side this season and is currently out of favour at the Riverside stadium.
Boro paid £1.5 million to Boca Juniors for the South American ace, but despite having immense talent, the winger has failed to command a regular first-team football during his time in the North East.
Torino have snapped up the youngster on a six-month deal, with a view to extending his contract for another season.
As Marinelli possess an Italian passport, he does not require a work permit and should go straight into Renzo Uliveri's squad after arriving on Sunday.
Meanwhile, Torino have signed Gualdo striker Paolo Bellucci although the youngster will not arrive in Turin until the summer.
The highly-rated hit-man will stay at Gualdo until the end of the season before moving to Torino.
