The man, 46, was knifed at Alexander Stadium in Birmingham at about 10:30 GMT, West Midlands Police said.
A 41-year-old woman has been arrested on suspicion of attempted murder. The man has been taken to hospital.
An area of the stadium, which hosts Diamond League events and the national championships, was cordoned off while forensic examinations were conducted.
Police said they were not looking for anyone else in connection with the stabbing.
A man suffered "life threatening" injuries when he was stabbed at one of the country's major athletics stadiums.