The 20-year-old Holland Under 21 international, who joined the Blues from Dutch side PSV Eindhoven in 2007, will go straight into the Foxes squad for their next Championship fixture which is at Sheffield United on February 1.
Van Aanholt has made eight first-team appearances for Chelsea, including four in the Champions League this season, and has Championship experience having enjoyed spells on loan at Coventry and Newcastle last term.
Van the man: Patrick van Aanholt has joined Leicester on loan
Leicester assistant manager Derek Fazackerley told the club's official website: 'Patrick is another quality addition to our squad. He is a talented young footballer with good skill, natural pace and the required hunger and desire to do well in the game.
'Although Ben Mee can play at left-back, Bruno Berner is our only specialist player in that position so this was an area we needed to add to.
'Patrick has impressed at Chelsea, Coventry and Newcastle and we are certain he will do likewise at the Walkers Stadium.'
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