The singer is being sued by John Urbano, who claims JT recruited him back in 2012 to shoot and edit a documentary film about the making of his third studio album.

According to the lawsuit, obtained by TMZ, Urbano claims Justin proposed an arrangement where he would share profits from the film with Urbano instead of paying him his normal fee -- but Justin shelved the doc, which is why the director feels he got the shaft.

Urbano claims he filmed Justin for a total of 60 days all across the world and spent about 2,500 hours editing the footage into a documentary titled, "The Making of The 20/20 Experience."

The director says if he had been paid on the front end for the project, his filming and editing fees would have reached $2,450,000 ... but he says the only money he's seen out of Justin is a modest $20,000 upfront fee, plus reimbursements for expenses incurred while filming. According to his math, Urbano's been paid just $7 per hour for the project.

Urbano claims Justin was moved by the documentary at first, but after his album became his most successful solo project he lost interest in the doc, which has never been released.

The problem for Urbano ... he says Justin promised to share profits with him, but if the doc sits on a shelf, the promise of a big payday goes out the window.

Urbano claims Justin used his network of agents, managers, and handlers to stop the director from getting paid ... and he wants compensation for an allegedly breached agreement.

The director wants Justin to cough up lots more money, and he also wants a judge to declare he owns all the rights to the documentary.