Lunt moves from Huddersfield to the Rhinos until the end of the season.
The 25-year old has been a key player for Huddersfield since making his Super League debut in 2009. He had previously played for Castleford in National League 1 and for Workington.
Lunt said: “I am at a stage in my career when I need to be playing regular first team rugby. I was surprised when Nathan Brown told me last week that Leeds had been in touch about coming here on loan. Normally when you go on loan it is not to another one of the top teams in the competition so I am really pleased to be joining the World Champions.
“My preferred position is hooker but I am happy playing in the back row as well, whatever the coaching staff want of me. I have trained with the Rhinos yesterday and the players really made me feel welcome.”