The British three-time Olympic medallist won the competition in 2010 and again last year and is well placed to defend his title this time around.
Fox-Pitt finished the dressage phase with a score of 33.3 penalties and holds a commanding lead over New Zealand's Andrew Nicholson who is second with Quimbo on 38.0 and third on Calico Joe in 40.8.
Chilli Morning is a 13-year-old British-bred stallion that Fox-Pitt has only been riding for less than a year, but he couldn't be happier with the pair's progress.
"He's got a great presence, and so when you're riding him you feel you're capturing the ground jury's attention," said 44-year-old Fox-Pitt of Chilli Morning.
"He paints a good picture throughout the test, and at this level you need to score well throughout the test.
"He's a very consistent horse, and he's very much with me in the ring. He’s a terrific horse to ride, and he did a lovely test.
"I've been very lucky to take on some horses later in their career, and I've gotten used to that. I quite enjoy it, actually.
"When a horse comes to you at the age of 12, like he did, you can't change them. You have to learn to get on with them. It’s good fun."