Nancy Mairs, whose encounters with mental illness, disease and religious faith found expression in a series of trenchant, intensely personal essays and memoirs, died on Saturday at her home in Tucson. She was 73.

George Mairs, her husband, said that the cause had not been determined, but that Ms. Mairs had struggled with multiple sclerosis for more than 40 years and had relied on a wheelchair since 1993.

Ms. Mairs was a budding poet in her late 20s, suffering from agoraphobia and depression — she had once attempted suicide — when she was told that she had M.S. The inexorable progress of the disease provided her with her richest subject, as she wrote of her fears and hopes, her resolve to push against her limitations and her aversion to such euphemisms as “differently abled.”

“I refuse to participate in the degeneration of the language to the extent that I deny that I have lost anything in the course of this calamitous disease; I refuse to pretend that the only differences between you and me are the various ordinary ones that distinguish any one person from another,” she wrote in the introduction to “Plaintext: Deciphering a Woman’s Life” (1986), the essay collection that established her as a fierce, funny, feminist voice. Her essays “On Being a Cripple” and “Sex and the Gimpy Girl” made the point, defiantly.

She looked at her life, and her infirmities, with an unblinking eye in a series of memoirs that included “Remembering the Bone-House: An Erotics of Place and Space” (1989), “Carnal Acts” (1990), “Voice Lessons: On Becoming a (Woman) Writer” (1994) and “Waist-High in the World: A Life Among the Nondisabled” (1996).

In two memoirs, “Ordinary Time: Cycles in Marriage, Faith and Renewal” (1993) and “A Dynamic God: Living an Unconventional Catholic Faith” (2007), she described her conversion, in her 30s, to Roman Catholicism, and the ways her newfound faith shaped her mental world and her attitude toward suffering, death and the social fabric.

“To view your life as blessed does not require you to deny your pain,” she wrote in the introduction to “Carnal Acts.” “It simply demands a more complicated vision, one in which a condition or event is not either good or bad but is, rather, both good and bad, not sequentially but simultaneously. In my experience, the more such ambivalences you can hold in your head, the better off you are, intellectually and emotionally.”

She was born Nancy Pedrick Smith on July 23, 1943, in Long Beach, Calif., where her father, John, a naval officer, was stationed. He died when she was 5 after driving his jeep over an embankment in Guam, where he had been transferred after World War II. Her mother, the former Anne Pedrick, took the family back to the United States, where she eventually settled in Wenham, Mass., north of Boston, and found employment as the village tax collector.

Ms. Mairs earned a bachelor’s degree from Wheaton College in Norton, Mass., in 1964, a year after she married. In addition to her husband, she is survived by a daughter, Anne Mairs; a son, Matthew; a sister, Sally Caroline; a half sister, Barbara Cutler; and three grandchildren.

She worked as a publications editor for the Smithsonian Astrophysical Observatory in Cambridge and the International Tax Program at Harvard Law School before enrolling in the University of Arizona, where she earned an M.F.A. in poetry in 1975 and a doctorate in English in 1983, presenting as her dissertation the book later published as “Plaintext.”

She published two collections of poetry, “Instead It Is Winter” (1977) and “In All the Rooms of the Yellow House” (1984), before finding that the essay was her métier.

As “Plaintext” made clear, she could write movingly about nearly any subject.

She plumbed the psychic lower depths in essays like “On Touching by Accident,” about her suicide attempt, and “On Living Behind Bars,” about her struggles with mental illness, but her determination to live fully and her sense of adventure infused many of her essays with an infectious zest.

Her disabilities, and the predicaments they spawned, struck her as amusing as often as not. “Where I Never Dreamed I’d Go, and What I Did There,” included in “Carnal Acts,” described an improbable trip to Zaire (now the Democratic Republic of Congo), undertaken against all advice. Ms. Mairs saw much of it as an exercise in comedy.

“She’s not telling these stories to inspire people or induce our pity,” the poet Kathi Wolfe wrote of “Waist-High in the World” in The Progressive. “The author is coming out from behind the curtain to make visible the experience of being disabled in America.”

A lifetime of disease and suffering led her, almost inevitably, to write “A Troubled Guest: Life and Death Stories” (2001). In a series of linked essays, she examined the deaths of her mother and stepfather, the plight of the death-row prisoners with whom she corresponded, and the unsolved murder of her foster son, Ron DuGay, at 41 in 2000.

Her interest, she wrote in one of the book’s essays, “A Necessary End,” lay in “the role of affliction in perfecting human experience.” Viewed from a spiritual perspective, she added, it is “simply an element in the human condition, to be neither courted nor combated. To refuse to suffer is to refuse fully to live.”