Mary Tyler Moore, whose witty and graceful performances on two top-rated television shows in the 1960s and ’70s helped define a new vision of American womanhood, died on Wednesday in Greenwich, Conn. She was 80.

Her family said her death, at Greenwich Hospital, was caused by cardiopulmonary arrest after she had contracted pneumonia.Ms. Moore faced more than her share of private sorrow, and she went on to more serious fare, including an Oscar-nominated role in the 1980 film “Ordinary People” as a frosty, resentful mother whose son has died.

But she was most indelibly known as the incomparably spunky Mary Richards on the CBS hit sitcom “The Mary Tyler Moore Show.” Broadcast from 1970 to 1977, it was produced by both Ms. Moore and her second husband, Grant Tinker, who later ran NBC and who died on Nov. 28.

At least a decade before the twin figures of the harried working woman and the neurotic, unwed 30-something became media preoccupations, Ms. Moore’s portrayal — for which she won four of her seven Emmy Awards — expressed both the exuberance and the melancholy of the single career woman who could plot her own course without reference to cultural archetypes.The show, and her portrayal of Mary as a sisterly presence in the office, as well as a source of ingenuity and humor, was a balm to widespread anxieties about women in the work force.

It modeled a productive style of coed collegiality, with Ms. Moore teasing out the various ironies known to any smart woman trying to keep from cracking up in a world of scowling male bosses and preening male soloists.