Morgan Pressel opened with a 6-under 66 on Thursday to grab a share of the lead after one round of the Women's British Open.

Pressel, the 2007 Kraft Nabisco winner, was joined atop the leaderboard by Camilla Lennarth, who is making her first LPGA Tour start. The duo tops a crowded leaderboard on the Old Course at St. Andrews.

Stacy Lewis and Na Yeon Choi, the second and fourth ranked players in the world, share third place at minus-5. They were joined there by 2009 U.S. Women's Open winner Eun-Hee Ji, Nicole Castrale, Mi Jeong Jeon, Sydnee Michaels and Ryann O'Toole.

Paula Creamer, who finished third last year at Hoylake, and 2009 champion Catriona Matthew carded 4-under 68s. They stand alongside Pernilla Lindberg, Dori Carter, Liz Young, Danielle Kang, Lizette Salas and amateur Georgia Hall in 10th place.

World No. 1 Inbee Park is looking to become the first golfer, male or female, to win the season's first four majors. She carded a 3-under 69 and is tied for 18th with 19 other golfers.

Park, who has six wins in all this year, was well en route to at least sharing the first-round lead as she had six birdies through 10 holes and was atop the leaderboard. However, she stumbled to a bogey at 13. Park followed a double bogey at 16 with another bogey 17 and a birdie at the last to post 69.

"I played very good on the front nine and then I had a little bit shaky on the back nine. But I still feel really good about the game. I was 6-under through 10 holes and that means I could do the same thing tomorrow," stated Park. "There was a couple of bad drives and a couple of bad putts on the back nine, but it's the first round. A little bit disappointing, but I'm glad that I've done that in the first round instead of the final round."

Pressel shared third place at the LPGA Championship earlier this year, but has just one other top-10 finish this season. She got off to a quick start with a birdie on the first.

The 25-year-old kicked in a short birdie putt on No. 5, but found sand off the tee at the sixth and that led to a bogey. Pressel stuffed another approach shot inside three feet at the ninth and tapped that in for birdie to make the turn at 2-under.

Pressel, who tied for 43rd last year after a final-round 81, converted a 10- footer for birdie at the 11th. After a par on the 12th, she caught fire.

The two-time winner on the LPGA Tour drained a 20-footer for birdie at 13. Pressel grabbed a share of the lead when she got up and down for birdie from just in front of the green at the par-5 14th.

Pressel grabbed the lead by herself at 15. She found fescue off the tee, but hit a stellar second shot within 15 feet and made that for birdie. Pressel closed her round with three pars in a row.

"I felt good out there. I knew I could shoot 6-under out here at St. Andrews, and nice to get off to a good start in this tournament," Pressel said. "I was very happy that it really only rained on us for one hole at most. Right after the rain, the wind actually switched to maybe a little bit of a different direction and kind of calmed down and that made our back nine play a little bit easier."

Lennarth, who Monday qualified for this championship, also started with a birdie at the first. After a three straight pars, she birdied the fifth.

The Swede, whose best finish on the Ladies European Tour this season was a share of fourth in the Netherlands, dropped in back-to-back birdie chances at nine and 10 to get within two of the lead.

Lennarth birdied the par-5 14th to move into a share of second place. She birdied the last to end alongside Pressel.

"First time at St. Andrews and first time at the British Open," Lennarth admitted. "I'm very satisfied, definitely. I hit all the fairways and all the greens, and it went pretty smooth out there. I actually think the highlight was I made birdie on the first hole. I felt like, OK, well, I'm at least going to make one birdie."

NOTES: Defending champion Jiyai Shin managed a 1-under 71 and is tied for 54th place ... In all, 73 of the 144 players posted scores in red figures ... Hall and top-ranked amateur Lydia Ko started with 68 and 69 respectively, and are the leading amateurs through one round.