The Serie A champions have already pilfered one starlet from the United academy, snapping up Frenchman Paul Pogba on a free transfer last summer.
And they're keen to do the same with Januzaj - United's highly-rated 18-year-old attacking midfielder.
Januzaj broke into the United first-team set-up over the summer after winning the club's reserve team player of the year award last season.
United boss David Moyes and his predecessor Sir Alex Ferguson attempted to persuade Januzaj to commit his future to the club, but the teenager is yet to agree terms on a new contract.
The report claims Januzaj's representatives are aware of interest from Juve boss Antonio Conte - and the Italian wants to take advantage of the contract stalemate to agree a deal in the January transfer window.
The United teenager is believed to want improved terms that reflect his new standing as a first-team player. He made his Old Trafford Premier League debut in the 2-0 win over Crystal Palace earlier this month, and is keen to receive assurances of playing time at the club.
But Juventus can point to the experience of Pogba, who left United for first-team football in Italy and has since flourished.
And the Serie A champions are not the only top-level European club interested in Januzaj - the report claims Barcelona and Manchester City have both been alerted to his potential availability as well.