The much-anticipated announcement was made Wednesday in a news release from co-owner Jess Jacksons Stonestreet Farms.
The sensational filly beat the boys in the Preakness for her sixth victory in a row, and has been in training at Churchill Downs.
The 1 1/8-mile Mother Goose is for 3-year-old fillies. Rachel Alexandra is expected to arrive at Belmont on June 23. In her last race against fillies, she won the Kentucky Oaks by 20¼ lengths.