The Welsh international was out-of-favour in Turin having played just 112 minutes this season.
Juventus were keen to get some of the 31-year-old's wages off the books and Rangers will reportedly pay around £2 million to take him to Glasgow.
Ramsey could be handed a baptism of fire away to Celtic in the Old Firm derby on Wednesday.
"I am really pleased to be joining a club like Rangers, where there is so much to look forward to between now and May," said Ramsey.
"I had a number of offers on the table, but none matched the magnitude of this club, with European football and the chance to play in front of 50,000 fans every other week.