The 19-year-old has enjoyed an impressive breakthrough season at United, making his debut in August's Community Shield triumph over Wigan at Wembley, just months after being named Reserve Player of the Year in May 2013.
Januzaj has since gone on to make 32 appearances for the Reds this season, scoring four goals, including two strikes on his first league start against Sunderland back in October, which announced his talent to the wider football world.
There had been press speculation about which international team Januzaj would play for. However, the Belgium-born youngster has always insisted his initial focus was on breaking into the United first team.
Marc Wilmots, head coach of the Belgian national team, confirmed the news of Adnan's international availability on Wednesday afternoon, while Januzaj verified those comments this evening via ManUtd.com.