The 22-year-old has secured a move to Anfield after falling down the pecking order with Jose Mourinho's Chelsea side, becoming Brendan Rodgers' eighth signing of the summer.
The 22-year-old passed a medical at Anfield on Monday and becomes the club's eighth signing of a busy summer of transfer activity for Brendan Rodgers' men.
The Nigeria international joins Mamadou Sakho and Tiago Ilori in joining Liverpool on deadline day, although Fabio Borini is close to leaving Merseyside for a loan move to Sunderland.
"First and foremost, I'm delighted to have made the loan from Chelsea to a big club like Liverpool," he told the club's official website. "The most important thing is for me to be professional about it and I'm here to do a job for the club.
"The target is to get into the top four and for the club to compete in the Champions League - and I'm delighted to be here. The manager has done very well and the formation and players here will help me and I just want to gel in, get to know the players and play with them.
"There are a lot of quality players here - they're winning games and creating chances. It's a massive thing for me to be here."
Moses moved to Stamford Bridge from Wigan last summer, making 42 appearances and scoring 10 goals.