Naylor has made 375 appearances for the Tractor Boys but has not played since last December's 2-2 draw at Coventry.
Simon Grayson said on the club's official website: "He's a good, strong centre-back and has got plenty of experience. He's played plenty of games in the Championship this season. He will bring a wealth of experience and he brings a lot that I believe will help."
Naylor told Ipswich's website: "It's a great opportunity for me to go and play some first-team football at a club that is obviously very close to my heart. I am really looking forward to it and hopefully I can help Leeds move up the table in the time that I am there."
Naylor previously spent time out on loan at Millwall and Barnsley in the 2001/02 season.