The 21-year-old, who made his debut off the bench in England's victory over Fiji, beat Alex Goode, captain Chris Robshaw and second row partner Geoff Parling to the award.
Launchbury made his England debut as a replacement in the victory over Fiji and he also made an impact off the bench against Australia to earn the starting jersey for the game against South Africa and the record 38-21 triumph over New Zealand.
The award was voted for by supporters on qberugby.com and
Launchbury said: "To win this award is massively humbling and I'm grateful to everyone who voted - to be honest I was shocked to even be shortlisted.
"It's been an amazing month for me, to make my debut in that first QBE international against Fiji was a massive honour - and at the time the biggest achievement of my career - but as the weeks went by I felt like I grew in confidence and for it all to culminate in that amazing win against New Zealand topped it all off.
"As Tom Wood said after the New Zealand game, although he won man of the match, any number of players could have taken the award, and that's exactly how I feel picking up this award.
"You're only as good as the 14 players around you and even when our backs were against the wall we stuck together."
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