United were granted a place in the second tier of English female football after announcing earlier this year they would be launching a women's team.
United had come under fire for not running a senior women's side, in marked contrast to Premier League rivals Chelsea, Manchester City, Arsenal and Liverpool.
But they signalled their intent to make a mark by appointing Casey Stoney, who won 130 caps for the England women's team, as the manager of their new side.
The seriousness of their intent to establish themselves in the women's game has been underlined by the recruitment of goalkeeper Chamberlain and defender Greenwood, regular members of the England squad bidding to qualify for next year's World Cup, from arch-rivals Liverpool.
"We've gone young, we've gone exciting, we've gone entertaining," Casey told United's website.
"I'm more than aware that we're bringing 21 strangers together but I'm really excited about the squad and the future of this team," she added.