O. Ruth Russell, 81, psychologist, educator and proponent of legalizing euthanasia, died Friday at her home in Chevy Chase. She suffered from Paget's disease, a bone disorder.

Before coming here, Dr. Russell was chairman of the psychology department at Western Maryland College in Westminster from 1949 to 1962.

During the last two decades,she had conducted an extensive educational campaign in this country and Canada to bring about legislative approval of euthanasia. In 1975 she published a book, "Freedom to Die: Moral and Legal Aspects of Euthanasia." It received testimonials from many professionals.

She received the Humanist Pioneer Award of the American Humanist Association in 1977 and also was active in the National Commission for Beneficient Euthanasia, the Euthanasia Educational Council and the Society for the Right to Die.

Dr. Russell was born in Delta, Ontario. She was a graduate of the University of Toronto and received a doctorate from the University of Edinburgh in Scotland. She also studied in Vienna.

After a career of teaching and research in her field in Canada and of serving as a personnel selection officer for the Canadian Women's Army Corps and the Department of Veterans Affairs in Canada, she came to this country in 1947.

She was an assistant professor of psychology at Winthrop College in Rock hill, S.C., before joining Western Maryland College.

Dr. Russell was a fellow and former director of the International Council of Psychologists, a fellow of the American Psychology Association, and a member of the American Association of University Women and the American Association of University Proffessors.

She is survived by a brother, Harrison Russell. CAPTION: Picture, O. RUTH RUSSELL