Ingeborg Day (née Seiler; November 6, 1940 – May 18, 2011) was an Austrian–American author who wrote the semi-autobiographical erotic novel Nine and a Half Weeks which she published under the pseudonym Elizabeth McNeill and which was made into the 1986 film of the same name starring Kim Basinger and Mickey Rourke.
In 1957, as a high school student, she participated in the AFS exchange program, living with an American family for one year and attending Eastwood High School in Syracuse, New York.
She met and married a trainee priest named Dennis Day, and they moved to Indiana, where she attained a B.A.
in German studies from Goshen College, and spent several years teaching in Kenosha, Wisconsin.
Day left her husband and moved to Manhattan with artist Tom Shannon and became an editor at Ms magazine.