Ian Poulter, who held the lead after 36 holes, carded a 3-under 69 to finish two shots off the lead at 19-under-par 197 along with Carlos Rodiles.
Choi, who was recently chosen as a captain's pick for the upcoming Presidents Cup, has displayed his talent in the United States with two PGA Tour victories in 2002 and now seems poised to add his name to the list of champions on the European Tour.
'Even as we speak now I know people back home in Korea are watching,' said Choi. 'Golf has become so popular now that whenever I play, I know TV stations are quick to take the satellite feeds and put the pictures out.'
The Korean began the day in a tie for fifth at Golf Club Gut Larchenhof and picked up a birdie at the opening hole. He then converted a five-foot putt for a birdie at the third before birdies at the seventh and the ninth moved him to 17-under around the turn.
Choi picked up steam on the back nine and took the lead for the first time with an eagle at the par-3 13th.
He added a birdie at the 15th and knocked his tee shot inside five feet for a birdie at the par-3 16th to regain the top spot at minus-21.
Choi made it three in a row with a birdie at the 17th and managed to hold on to the outright lead despite a bogey at the last.
'Generally the course fits me very well,' said Choi. 'The wind can be a factor, but if I hit my shots well, then the style of the course suits me.'
Jimenez was near the top of the leaderboard all day and jumped out of the gate with an eight-foot birdie putt at the first. He then two-putted for a birdie at the par-5 third and landed his approach within 10 feet of the cup for a birdie at the fifth.
The Spaniard stumbled with a bogey at the sixth but recovered with a birdie at the very next hole. Jimenez then found himself in sole possession of the lead at 18-under par after playing partner Poulter missed the green at the 10th en route to a bogey.
Jimenez fell one back of Choi's charge but regained the advantage with an eagle at the 13th. He kept pace with a birdie at the 15th but found trouble with a bogey at the 16th.
Jimenez recovered with a birdie at the last to finish within one of the lead.
'Going into the final round, I will try and play well again and try and do the things that I did well today,' said Jimenez, who shot a 67 on Saturday. 'I much prefer to play in these conditions and temperatures which are like Malaga, but there are still a lot of players in contention who can win the tournament.'
Paul Casey posted a 5-under 67 to finish four shots off the lead at 17-under-par 199.
Niclas Fasth and Jarrod Moseley were one shot further back at 16-under-par 200.
Retief Goosen, who captured last week's Trophe Lancme, joined Darren Clarke, Fredrik Jacobson, Mark McNulty, Gary Orr and Miles Tunnicliff in a tie for eighth at 15-under-par 201.