Ryo defeated Seo Hee-kyung in a playoff last year to win the U.S. Women's Open. She'll be joined with 2010 champion Paula Creamer and 2009 winner Ji Eun-hee for the first 36 holes of next week's tournament.
They are to start from the 10th tee at 9:06 a.m. EDT Thursday.
Starting at the same time at No. 1 is a group that includes two-time U.S. Women's Amateur winner Danielle Kang, who has since turned professional. In her group are Natalie Gulbis and Lee-Anne Pace.
Four of the Top Five-ranked players in the world have Thursday afternoon starts. That includes World No. 1 Yani Tseng, who has won five major tournaments but never the U.S. Women's Open. She's grouped with Choi Na-yeon and Suzann Pettersen, who are fourth and fifth in the world.
The 2012 U.S. Women's Open is being played at Blackwolf Run in Kohler, Wis.