Whitney North Seymour Sr. (January 4, 1901 – May 21, 1983) was an American attorney who worked primarily as a trial lawyer.

Seymour served for many years as the managing partner of the law firm Simpson Thacher & Bartlett.

[2] He was an assistant solicitor general in the United States Justice Department from 1931 to 1933 before returning to Simpson Thacher & Bartlett.

He served as president of the Legal Aid Society, the New York City Bar Association, and the American College of Trial Lawyers.

He was particularly active in organizations dedicated to historic preservation, and he was an active member of Grace Church in Greenwich Village, where he led the committee which saved the James Renwick designed facade of the Grace Church School.