Bruenig was born in Arlington, Texas.^[2] She attended Martin High School.^[3] She graduated from Brandeis University in 2013 with a Bachelor of Arts degree with a double major in English and sociology and a minor in Near Eastern and Judaic studies.^[4] As a recipient of the Marshall Scholarship,^[5] she studied at Jesus College at the University of Cambridge, where she earned a Master of Philosophy degree in Christian theology^[6] under the supervision of John Hughes.^[7] She was named a 2014–2015 Presidential Fellow at Brown University, where she was a doctoral student in religious studies,^[8][9] but left Brown without a degree in 2015.^[10]

Bruenig was an opinion writer and editor for The Washington Post,^[11] The New York Times, and now writes for The Atlantic. She writes about ethics, politics, theology, and economics.^[12] Previously, she was a staff writer for The New Republic.^[13] With her husband Matt, Bruenig co-hosts a podcast The Bruenigs.^[14] In the past, they have written together for The Atlantic.^[15] She has also been a contributor to the Left, Right, & Center radio show.^[16][17] On May 12, 2021, it was announced that she would depart The New York Times for The Atlantic at the end of the month.^[18]

In a profile published by Washington Monthly, she is described as "the most prominently placed of a small but increasingly visible group of young writers unabashedly advocating for democratic socialism."^[19] In an article in Deseret News, Lois Collins described Bruenig as "just left of Bernie Sanders on economics, openly religious and quietly anti-abortion."^[20]

In September 2018, Bruenig described a 2006 sexual assault on a woman by the name of Amber Wyatt at Martin High School in Arlington, Bruenig's own alma mater, in a story for the Post, describing the assault's repercussions.^[21][22] She started tracking the details of Wyatt's story in 2015.^[3][23][24] In 2019, Bruenig was named a Pulitzer Prize finalist in Feature Writing, for one of her pieces covering Wyatt's sexual assault, "What Do We Owe Her Now?"^[21] The citation reads: "For eloquent reflections on the exile of a teen sexual assault victim in the author's Texas hometown, delving with moral authority into why the crime remained unpunished."^[2]

Bruenig was named in the 2019 edition of Forbes magazine's 30 Under 30 list.^[25]

Bruenig was raised Methodist, but converted to Catholicism after studying Christian theology and the work of St. Augustine of Hippo in university, becoming confirmed into the Catholic church in 2014.^[20][26] Bruenig married Matt Bruenig, whom she met in their high school debate team in Arlington,^[19] in 2014.^[27] They have two daughters together.^[20]

• "Taking Augustine as Guide". In Schwindt, Daniel (ed.). Radically Catholic in the Age of Francis: An Anthology of Visions for the Future. Valparaiso, Indiana: Solidarity Hall Press. 2015. ISBN 978-0-692-40977-0.
• "Church". In McElwee, Joshua J.; Wooden, Cindy (eds.). A Pope Francis Lexicon. Collegeville, Minnesota: Liturgical Press. 2018. pp. 15–17. ISBN 978-0-8146-4545-1.